I have noticed alot recently that people are not turning up to or leaving the first frame of a multi frame game so to stop the chance of losing more rank... is this bad sportsmanship?

Ohhhhhh well spotted

ive noticed too however in some cases you don't know if someone got disconnected or left intentionally.

I don't think this is a systemic problem at all as most non-attendance DQ's tend to be in the lower rounds (where it is a single frame anyway) or in higher rounds where the opponent has had a bye (in which case they may have been logged out due to the wait).

In the cases where that is the thinking, it isn't so much 'bad sportsmanship', but rather 'bad logic'. This is because no matter who you are playing, there is always the possibility of winning at least one frame in which case it is entirely possible that ranking points could be gained even by losing overall or at least mitigating the outright loss.

Also, and I hate to say this, but the people who are most obsessed about what ranking points they win/lose are those that are the higher ranks anyway and giving up ranking points to a lower ranked player is just nonsense.