I think it's because near the end of "The Mom Who Loved Me", the narrator said "Not a bad guy, plot twist or spy mission to be found.", so since Season 2 has no cliffhanger(s), I think the series is done for good.

@A3OfWillow yeah, but while the ending was happy and all there is a little question the series failed to answer: Who wanted Sam terminated and why?

Probably Philip Trousers, considering that he was his/Pam's enemy.