Too many of my miles are on hard surfaces. Running on hard surface can lead to injury; your body recovers faster from running on softer surfaces. The injuries you could get in this manner are usually bad, ie stress fractures in your legs. There are pros who run entirely on pavement and pros who run entirely not on pavement. Most pro road racers include some pavement running since thats what they'll be racing on, but their lifestyle (ie being paid to run) allows them to sleep in and optimize daylight to do their runs on trails as well as live near good trail systems.
You're better off running on pavement than choppy grass. Just before the marathon boom, at the start of the early 2000s high mileage boom, everyone was talking about getting off the roads as much as possible. But that sort of went by the wayside when everyone wanted to start doing marathons instead of xc races and track races. Its still probably a good idea to do as much trail running as you can though, if you have good trails near you.