It's because everyone hates the neverending season of Rockpox and they're doing it in response to people talking about how unfun it is. It's going to be a good feature.
This is great! I have never had much time to pour into it, and tbh when season 4 came out I pretty much dropped the game because I felt like I wasn't going to be able to play enough to make it feel worthwhile. Now I can go back to the start and just pick away at it! Brilliant!
DRG made an effort with all of their seasons to make sure that players wouldn't be locked out of cosmetics or other rewards. I'm not surprised that they wouldn't want people locked out of experiences either.
Glad they are doing this. I don't mind seasons too much, but I start to feel kinda exhausted if the station or maps are just completely overwhelmed by seasonal changes and not just the base game stuff.
I do hope they add more mission types eventually. Would like to see kinda...L4D2-style "Get from PT A to B safehouse" before completing a major objective deeper in with limited supplies. Deep dives feel too much like standard missions in this regard, to me. I'd like to see more variety, at least.
Underground lakes, rivers, and water sounds that affect navigation or gameplay could be interesting, too. Pondskater enemies, diving sections, etc.