A lot of people are simply trained to work, play, eat, or do whatever the way they do it now. Doing it differently requires them to actually train something new. It requires concentrated effort. That's not easy for many adults. It's hard to break out of the deep ruts we build for ourselves over years and years.
Bad habits are formed exactly the same as good habits, but what you consistently do. For recreational players weak fitness causes us to compensate with reaching, leaning, falling backwards, etc. instead of forcing ourself to get into proper position and setup. So we get good at compensating, and some really good at it when we see those awkward strokes in 4.0 and maybe some in 4.5, but it is the most limiting factor for adult players. Interestingly I was just talking with a few of the college kids when I was doing a light hit with them about NOT hitting with lower players too much because the more often they do it, the more they end up playing down and that can also form bad habits.
I found it REALLY has effected me having not played at level or up for quite a few years now and helping with the high school and juniors players, that I have gotten both physically and mentally lazy and I caught myself with all the bad habits that forms in a recent match against a higher player getting bagelled the first set, grabbing a few the second, and like 1 the last set. Was a stark reminder that as much as I like hitting with anyone and everyone, if I do really want to continue to improve (still not 100% convivnced I care right now) I need a higher level of practice and play more often. I am impressed that full time coaches can hit with all those various levels and still manage their own game too.
Anyway, back to ball height, I found the video I did from a past thread on this. I went our to see how I could vary height and depth, and the first three or four shots are my basic neutral rally ball shots, but then I tried hitting flatter. On all shots the goal was service line or back for depth. As you can see, as I flatten out I start dumping in the net, so there is a diminishing return for me when trying to hit flat often. I also notice I was trying not to hit long when hitting flat, and consequencly I hit more topspin and looks like they were dropping short.