Alot of thought went into this choice before making it.
Some basic reasons like:
-It'd obviously make SA-Sonic more OP, and we were treading that line already
-It'd be overkill easy to both get and uphold Super Sonic
-It'd destroy multiplayer special stages
-It can interfere with infinitely more important actions. You NEVER want to lightdash when you meant to spindash/bounce, or have to stop yourself from doing so because rings are in the way.
-People need to bind more custom buttons to play SA-Sonic properly if I made it a custom button.
-This method prevents players bouncing into pits instead of lightdashing due to of depth perception, which never feels fair.
But there's other specific design reasons relating to SRB2's ring placement.
In an SRB2 context, a rapid lightdash is a novelty that might either be OP or useless depending on SRB2's hugely varying levels, none of which place rings with a lightdash in mind. This leads to Sonic spazzing around if you nonsensically lightdash on weird ring patterns, which alot of players will do anyway just for free rings, and it looks "le funny"
But when you need to charge, you think
about what you're doing and where you'll end up. You consciously make decisions and choose ringtrails benefitting your movement, rather than zoom across any random ring pattern for ez rings. The Lightdash is meant as a movement
tool. If I encourage lightdash spam, I also encourage SA-Sonic to spazz across unpredictable ring patterns, slow himself down and change direction all the time, and accidents where you're flung into walls and traps. I can't make the lightdash range less reliable either just to make it more situational. SA2 and Heroes' lightdashes are both awful for that reason.
Plus, if you can use it on-the-run, I have to make another
choice. Do I allow players to potentially fly out of control if I retain their potentially superfast momentum into these unpredictable ring patterns? Or...do I slow them down in an unsatisfying way because it'll go at a set speed? I can't win in that respect. But momentum isn't an issue with the charged version. Both the player and I know what speed they'll be entering the ringtrail at, giving both of us a more predictable pattern to react to.
Try using the quick-charge and this lightdash version's boosted chaining potential. (Sonic can ALWAYS charge or jump from a lightdash, even in midair.
) You'll come to see that the Lightdash I gave SA-Sonic, while not spammable, is more versatile than it's been in any game. If for whatever reason you STILL can't deal with it, add a general lightdash mod like this one: https://mb.srb2.org/addons/1-09-4-light-dash-port.2813/