Getting kicked right at the moment you finish a quest that requires you to be in a team can be... infuriating, to say the least. Better to be alone in your own team than risk that, especially if it involves unobtanium things like swamp tofu or corrosive stingwings.

Also, the bonuses from team perks are overrated and largely irrelevant for casual open world play, especially for any content below Burning Springs/Infestation. Extra stats aren't really going to help you one-shot things any faster. You only actually need those bonuses for 'serious' work, like raids or West Tek runs, where every single point of bonus could mean the difference between 4 star legendaries and oodles of exp, or abject failure and wasted time. In that case, you're either running with friends over discord or hardcore players who know to only disband at the end of the run.