Don't think it was cancelled simply because the ending was pretty meh and nonconclusive. I've seen so many titles that end on mediocre endings and many artists simply can't write them.
Like, I like Satoru Takamiya's work a lot but every single thing this artist has made ends on a nonconclusive bad ending that doesn't feel like an ending. I sincerely doubt that everything this artist makes is cancelled when a new serialization starts one month later and they're all about 20 chapters; some artists simply can't write endings well and it seems to be the most difficult part of the trade. I read so many magazines wherein artists have stories of about 15-20 chapters with so-so endings and then start a new serialization again the next month.
However different this was from Boy Skirt, it had the same problem in that the ending amounted to nothing. The ending didn't even really feel rushed, simply nonconclusive and incredulous.