...You're still doing it.I didn't mention that before, as the previous post was only a bug report, since they for some reason belong in suggestions...?
What you're suggesting is to change a core gameplay mechanic so that you have an easier time playing the game. This is not a bug report.
The way SRB2 works, and how it mimics the classic Sonic games is that if you're jumping and have (sufficient) upwards momentum, and you let go of the jump button, this causes your momentum to drop. (In practice, I believe SRB2 halves your momentum while the original games set it to a fixed value.) This mechanic exists to give you control over your jump height: the sooner you let go of the button, the quicker the momentum cap kicks in and the shorter your jump becomes.
However, the way this mechanic is implemented also means that if you jump on something from a great height and hold the jump button while you bounce back up, you will rise all the way back to your original height (plus the added force from your jump), since the bouncing physics simply reverse your vertical momentum. This is a very important tactic in advanced play, as it greatly increases the movement options you may have at any given time.
Those options then increase tenfold when you add in the momentum cap, since over such a long rebound, you have a wide range of points in which to let go of the jump button and dramatically change the height and shape of your jump arc. Sometimes it's useful to go back up to the height you started at so you can reach something which was at the same height, but too far away horizontally. Other times, it's more useful to cut your jump short so you can quickly go in a tunnel or hit an enemy or simply land on the floor quickly.
tl;dr Allowing you to CHOOSE how high you want to jump is much more important than saving you the chore of remembering whether you're pressing the jump button or not. And at the end of the day, SRB2 aims to emulate how the classic Sonic games played and the movement choices present therein, only straying away when balancing the characters for multiplayer purposes, such as Tails' downflight.
(Though one thing that's always bugged me is how easy it is to cancel a spindash. It was a one-frame trick in the originals, while in SRB2 it's actually easier to jump out of a spindash then launch one at minimum speed. Manual spindash charging when?)