When I first started doing more trail riding, I got a giddy up mounting stool. It was very handy, I could put it in my saddle bag and get on with no problems(it is about 11inches high which helps alot) Since I trail ride so much now, I have taught my mare to stand in ditches, near rocks, stumps, anything elevated. Sorry I couldn't get my computer to let me add the link. I found it on Amazon, but I'm sure I have seen it elsewhere for less.
I'm short and never liked mounting from the ground but HAD to when I was learning to ride (military, big warmbloods, I'm 5'3, *sigh*). Good thing that 1) I was young and athletic, and 2) these big horses stood stock still while I was hauling myself on board, lol.
But after that I never mounted from the ground if I could help it. I train all my horses to mounting from "objects". I have no shame. Whatever the object is, the higher, the better, so I don't even have to use a stirrup!
So...piled buckets, water troughs (in the paddock when mounting bareback to bring horsey in), boulders, tree stumps, flatbed trucks, the edge of a porch, a xc jump, picnic tables...anything goes! It is MUCH easier on the horse's back as well.
At 67+ I can still mount a 15.0 hand horse from the ground. It ain't pretty and is a strain on the horse and me, but it can be done.
Should it be done as a matter or routine? Probably not. It's easier on the horse and me with a mounting block/aid. But with any mounting aid you must train the horse to the aid. I see a lot of riders using a block and two assistants because they've not bothered to train their horse to stand quietly. If you're working a youngster (as I am) sometimes a "ground assist" is required. But the number of times should be steadily diminishing.
Agree with G's post above. I also occasionally dismount onto the mounting block, just so the horse has that skill- as used for example in therapeutic riding, or if one ever had a situation with someone with an injury for which gently dismounting onto 'higher ground' might be necessary.
When I first started re-riding, I could NOT mount my 16.3 horse from the ground. But the flexibility came back (even though I was in my 40s at the time!). Now both my horses are about 16.2, and I can mount them from the ground (it helps to have a little hill). Which I have found to be useful in case I drop my whip or make an unplanned dismount.