I think generally the most popular "porn" user is male, and the most common go-to for most men would be f/f be it tickling or anything, so I think the most of the tickling videos around are probably f/f. I understand there has been a purge of tickling videos in general recently, so if you lose half of an already smaller content it leaves you with even less. I think its just a symptom of the popularity of f/f tickling in general.
Me personally I would love to see a wider variety of all tickling videos, I love to see m/m tickling videos but they are very limited, and not overly popular