We have a tent carpet and it makes a big difference. They are very insulating and comfortable to walk and sit on.
Mine is soft material rather than the hard hessian type ones you can buy.
We've never had a footprint but I guess it keeps your groundsheet clean. Our groundsheet unzips from the tent making it easier to clean/hose down.
No need to buy "dedicated" footprints or carpets though. I use picnic blankets as carpets and a large tarpaulin for the footprint and overlap / fold to size as required.
The package we got with our Airgo Solus 4 included footprint and carpet. First time with both. Having the footprint means I can see where the tent will sit but the main benefit is that the underside of the tent stays mudfree.
Another big advantage of the footprint is that if you're camping with a few friends on a free-pitch campsite, and one of them can go up earlier (or you're at work and going up much later) they can take the footprint and stick that down to ensure you're all together.
Just be aware though - My friend has done this a couple of times and invariably forgets when placing the footprints that tents have guys...
When I bought a dedicated footprint for a tent it turned out to be too big so I had to cut it down. They are basically just tarpaulins cut to shape for your tent. So...just buy a tarpaulin nearest to the size of the base of your tent and cut it to fit yourself. It needs to be a few inches short all round so it does not stick out, and water cannot drip off the flysheet onto it and run back underneath.
They help to protect the base of your tent from sharp stones, thorns, and any other sharp stuff which you have not spotted on the pitch. They keep the bottom of the tent clean and dry and it is much easier to hose off or brush off a tarpaulin at home than struggling to clean the base of your tent. They also help a little with insulation. Also, when rolling up your tent to go home you will have a clean surface to kneel on.
There is nothing worse than stepping out of bed in the morning onto a freezing cold groundsheet. A carpet is a must for comfort, warmth and insulation.
A dedicated fitted tent carpet is nice but expensive. You can buy insulated picnic rugs which are made from the same materials as tent carpets so do the same thing at a fraction of the cost. You may have to buy a couple and slightly overlap them to fill the floor space but bearing in mind nobody walks right up to the walls of a tent except at the doorway, there is no need for them to be fitted wall to wall. You don't need the carpet to fit underneath tables or storage boxes either so you don't need to fill the entire floor space with carpet. Certainly a must in the bedroom for insulation underneath airbeds and for stepping out onto, and very nice in the living area where you walk.
I also use a doormat to blot or remove shoes, before stepping onto the tent carpet.
Footprints be they tent specific or just a tarpaulin, have a benefit that most overlook! - they stop the bottom of your tent getting wet and muddy AND (the overlooked bit!) they stop that wet/mud transferring to the canvas flysheet of your tent when you pack it up! Your tent stays cleaner and the lack of mud/muck helps preserve the waterproof properties of the topside canvas fabric. They do also offer some protection to the sewn in groundsheet, which you really don't want holes in.
Once you've had a tent carpet in whatever form, you are unlikely to want to do without one again, they do make it far more comfy in general, not just underfoot.
Place a large doormat or offcut of carpet just inside your door(s), it saves so much muck/grass/wet etc. walking throughout your tent. It's so much easier to shake it or brush it outside than trying to clean a whole tent or fitted carpet.
An 'under ground sheet' or footprint just helps have no/less holes in your ground sheet and ours is a sewn in one. Our footprint has several lots of duck tape on it to cover the holes, whereas our groundsheet of our tent does not have any holes.
A carpet means that you do not get holes in your ground sheet from the top. When are children are being silly they have done (& may again) lean back on their chair onto 2 legs. This puts pressure onto the groundsheet which may make a hole in it depending on the ground you have underneath you. Also toy cars, dropping a fork and in fact anything pointy could also ruin your groundsheet and its waterproof-ness so letting in water. A carpet stops some of the wear on a ground sheet.
Yep, there was no specific tent carpet made for our Cabanon or footprint for that matter, so I purchased a couple of EOL Outwell tent carpets and had them modified into bespoke carpets for the living area ZiG and bedroom pod SiG.
Also for use as a footprint I bought a bunch of cheap dark green tarps 4m x 5m from B&Q at £2 each they are cheap enough to treat as disposable.
On top of the cheap tarp goes 4m x 5m Butyl Rubber 1mm thick pond liner to act as under ZiG protector.
All I can say is that the ZiG and SiG for our tent are now in there 11th year, and are in as new condition.
I wouldnt be without either now, the footprint has saved the bottom of our tent from being wet and muddy several times and its much easier to put the footprint over the washing line and hose it down than the bottom of the tent.
We have the specific carpet for the tent in the lounge area and now we have bought a new tent we use the carpet from the old tent for the bedroom area, makes it so much cosier