If one restaurant has a "default" service charge of 10%, and another has 20%, it very probably will sway me to the 10% one, yes (these figures will be printed at the bottom of the menu, are normally added to your bill but you can ask to have them removed, and the menu will be at the door or window, visible from the street, I believe it's a legal requirement). But then tipping culture is different in the UK.
I understand what you're trying to get at - giving investment banks an incentive etc. - but the high degree of conformity doesn't make sense. Even large slices of small pies won't interest banks much, and similarly only a small slice of a huge pie ought to interest them plenty.
The point wasn't really so much about the incentive, but just that service fees are often cultural. Conformity doesn't come from economic forces, but cultural ones.
I think there's a big difference between service fees on a $10 dinner and a $100 million-$5 billion IPO. In particular the extent to which they are affected by custom is probably different considering the size of the sums. And the reason for the "tip" . . . nobody feels bad about giving an investment bank as little as they can get away with, but with tips it's a different story.
I understand what you're trying to get at - giving investment banks an incentive etc. - but the high degree of conformity doesn't make sense. Even large slices of small pies won't interest banks much, and similarly only a small slice of a huge pie ought to interest them plenty.