Splash screens are leftovers from the old-old days of text-based computing when you had to mask the fact that the program being loaded was going to take awhile (>30 secs).

Hardware, software, network, total users, i/o, it didn't matter, it was better to say something than let users sit there at a terminal thinking nothing's happening.

Or worse, tell their boss the "system's down again."

No excuse for them today. They just say "big app", it's gonna be awhile.