For a long time my fastest machine was a 800Mhz P3, wife and daughter had the newest machine, poor dad the old junk.
So following current by recompiling was not a viable option. Thus my preference for using pre-compiled stuff.
Also about release time the OBSD porters urge you to test the binary packages. That's another reason.
Reason nr 3: I don't mind being a 'guinea pig' ; the binary install sets sometimes contain 'uncommited patches'. One time Theo mentioned that a particular snapshot contained IIRC 11 patches, not anywhere to be found in CVS . Same way like they test new medicines with a double blind test
Now you understand why I never have an issue with "Flag Day". Maybe others can give their reason.