I believe Crash Bandicoot 4 on PC also requires Battle.Net client-app and an always-online Internet-connection to play.
Don't recall if they ever changed the stance on that.
Not familiar with the fourth installment but if it is anything like the previous mainline games then I will go ahead and assume that is always-online needed for singleplayer...lovely. Not that there is any excuse for multiplayer DRM either, but why is anyone buying this stuff at all? I get being a fan of certain series, but is it really THAT important to play another Crash Bandicoot sequel that it keeps wreaking havoc on the rest of us being able to own games?
Yes, it's single-player only.
This is done to try to make it look like they are preventing piracy and make sure gamers buy the game for $50-70. Why else? It's DRM being DRM; protecting the game to make sure they get sales or make it look like they are getting that, of course.
Things get more tricky if there's some files only server-side, Saves Cloud-side, and/or stuff of that sort. Probably would be a pain for hackers to reverse-engineer, to work offline.
Gamers are used to this treatment as they have all of these shiny features in their client-app on PC or on their console - Achievements, Online Co-Op/MP (if supported), Cloud Saves, etc etc.
Gamers often can't wait - and just buy stuff ASAP at $60-70. A lot of us here on GOG might not be of that club, but a majority of gamers do buy stuff on Pre-Order, Day 1, Week 1, or not too long after.
Dev's and pub's seem to be training gamers for the inevitable streaming-only gaming take-over, whenever that horrible inevitably comes.