If you’ll forgive the Seinfeldism, what’s the deal with “amusingly named” coffeeshops?
- Daily Grind
- Sufficient Grounds
- Perks of the Job
- Common Grounds
- Drinky the Crow’s Kaw-fee Hut (ok, not really)
Is it that people are more willing to take the terrible puns before they’ve had their coffee?
An Ergodic Walk 
More of the same:
morning due (in SF church and 17th)
brewed awakenings (on your side of the bay)
progressive grounds (on cortland in bernal)
bean there (lower haight)
And of course, the TV reference is not seinfeld, but Friends: central perks.
I think to constitute a “Seinfeldism,” you have to start with “Did you ever notice that . . .”
As far as the substantive question, it’s because the names are memorable. Even if you groan, you still remember it.
We used to have “Uncommon Grounds” once upon a time.