The 25% speed increase is so tiny (it would be the smallest speed boost in the game) but it doesn’t apply while self repair is active.
it only applies if you are healing while self repair is active.
What would it have cost to have this if it applied when self-repairing? Now you can’t do jumps without self-damage which Bastion cannot get.
Because they think that would be OP? Its only supposed to allow Bastion to retreat faster when a position becomes or is soon to become comprimise. If you could do it all the time you’d be able to get to the point 25% faster which doesn’t sound like much but it is actually quite alot especially on defense. On Paris, the one with the longest walk from Spawn to point A, it would reduce the time you needed to walk to point A from spawn on defense by 7.125 seconds or so. This is a pretty big deal. Getting there 7.125 seconds earlier means potentially being able to do 3206.25 more damage by the time the push ends. This is of course assuming the run head long into the bastion which they probably won’t do unless you are in sub 1000 sr bronze. More realistically you will prevent them from being able to use ults they would have been able to use otherwise as bastion is pretty good at shutting down alot of ults (reaper’s death blossom, Riptire, Bob (shoot it with one other person and you’ll shut it down pretty fast), Primal rage and Whole Hog). In the time you’ve gained from the speed buff you will probably be able to destroy the enemy team’s shield which will might cause them to have to wait another few seconds before being able to make the second part of the push after they get behind cover. This might not sound like much but these seconds can add up to a significant decrease in the time it takes for the enemy for the enemy to take the point (say 20 seconds or so if you die 3-4 times). And this isn’t counting in the fact it makes a bunker comp harder to dislodge. Usually you just have to kill the bastion but if the window to take control of the space bastion could attempt to set up in is 7 seconds shorter it will be significantly harder. Also bastion can climb things with this buff which allows him to get to a bunch of new positions ([Experimental] How streamers balance the game - YouTube) which becomes much much much more powerful if he can use it via just holding down left mouse button. If you still think this should happen that’s fine but this is the reason Blizzard didn’t do it.
TLDR: Because its a really large buff especially on defense if he can just hold down left click to get a speed boast. If you think Bastions nees a large buff fine but its pretty hard to deny 25% speed at basically all times in recon mode unless you are shooting (which you won’t be doing an awful lot of in recon mode) if a pretty large buff, much much larger than what they gave him. Plus I’m fairly certain these buffs only existed on OWL request, so they just let them balance the game essentially.
I’d prefer them to take more of an Yagorath approach to Bastion (the new stationary tank in Paladins).
She has a stationary mode and a mobile mode. While stationary she deals a lot of damage, then when she’s mobile to reposition or to scout, she deals less damage.
I don’t know if that could work for Bastion, but that sounds like a possible approach (I guess).
Its one of the few speed boosts in game and its a pretty decent one too, and it isn’t the smallest speedbost in the game, that’d be pharah’s thrusters it provides a 20% speed buff to herself
that’s kinda understandable since Self Repair doesn’t consume resource unless bastion is missing health meaning it’d be an infinite 25% speed boost while full health
but in the end it doesnt really matter i suppose the patch was never gonna go through
This reminds me of one of my oldest topics years ago before I realized he was untouchable Bastion Rework
I feel like heroes should be “experts” at their unique trait. For Bastion, that feels like transformation to me. Like Yagorath, I want to see him go tank mode mid battle to quickly reposition and then go Sentry to fire down a lane. (Tank mode shouldn’t just be like how it is in ult, though)
Transforming should feel like a much more fluid process – they actually buffed him that way years ago and it felt nice jumping and transforming in one smooth motion.
This speed buff idea sounds interesting but it also sounds like it just helps him retreat a bit better. Kind of makes Bastion sound like Chunky: 76 with a conditional sprint 
I’d rather he get changes that allows him to engage better without becoming Optimusprime: 76