As opposed to having a wallet full of bills and only have 25 bucks?![]()
25 $1 bills is a lot less annoying than 25 $1 coins.
But who ever carries around that many $1 bills\coins? Personally, I never have more than three or four loonies in my wallet at a time.
When I visited England about a decade ago, I often ended up with seven or eight pound coins before I was able to spend several of them (their bulk didn't help). I vastly prefer dollar bills to dollar coins. Coins are durable, but not very convenient.
(I probably have about $10 in Sacagawea dollars in my spare change tin right now.)

Perhaps the only down side to self service I've seen so far.
Perhaps they don't want small value coins stacking up too quickly, thus saving them maintenance costs. Bottom line business, gotta' love it.