You pretty much have to play during the first week or 2 of season launch to get out of low/zero MMR or you won't be able to play ranked for the rest of the season.

Possibly because of a combination of no rank reset each season (you pretty much never start a season in low MMR again after you make it out during the previous season) and everyone being under the impression of not being able to play ranked again after those first 2 weeks if they don't do it right away (FOMO).

SE has cemented FOMO into the playerbase so hard that it will be nearly impossible to convince people they don't have to bum rush content immediately on release lol.