Greetings 50+ friend. I have camped close to 1001 nights and never used a footprint. I never noticed a problem. I always prepare the ground by sweeping it with the side of my shoe. I get all the rocks and sticks out of the way. Have you ever slept with a rock under you? Not good. I think this also helps protect the tent floor against damage.

+1 on the not having the ground tarp stick out past the bottom of the tent. We went camping with another family on a spring break when it poured. They had a dome tent set up on a brand new green poly tarp that hung out about a foot all around. When the rain started, the water ran down the side of the tent, onto the tarp, and under the tent. They ended up with major puddle in the middle of their tent.

In big rain storms I use the old fashioned "trench" method to prevent the same sort of thing happening - water coming down the side of the tent, then going underneath. I dig a small trench around the perimeter of the tent - basically directly under the edge. When I car camp I bring a small gardening trowel, but I've done it with a stick many times. If the trench undermines the edge of the tent by an inch or two, no big deal; you don't really put any weight on that part of the tent anyway. When the water drips down the side of the tent it drips into the trench and stays there - usually to spread out along the trench or sink down into the ground. If there are any places where water seems to funnel, make the trench larger below it because it will get a larger volume of water.

Going to the trouble of digging trenches has kept my tent floor dry many, many times.

In real severe rainstorms on surfaces where the water can puddle up and over the trench and under the tent you have to dig an "escape trench" that leads to lower ground. I can remember three camping trips in the last 20 years where this became necessary.

Lastly, picking a good site for your tent is important. I learned this on my first Boy Scout backpacking trip (my first camping trip without my dad setting up the tents.) We slept on a tarp (with another tarp strung over us) and put it in a bowl. I slept in the middle. It rained and snowed. I slept in a puddle all night. Miserable!