Factions had developed among those Christians at Corinth, with each group built around a prominient Christian.This caused divisions and undermined unity of faith. Paul was pointing out that it wasn't important "who" conducted the baptism. And it should be noted that is doesn't say these people weren't baptized.
Why would Jesus say: Whoever believes and is baptized will be saved; whoever does not believe will be condemned. Mark 16:16
So, they were baptised.
1Cr 1:15 Lest any should say that I had baptized in mine own name.
Of course. People are only baptised in the name of the Father, the Son, and the Holy Ghost.
1Cr 1:16 And I baptized also the household of Stephanas: besides, I know not whether I baptized any other.
St. Paul did baptise an entire household, he would not have done this if it wasn't important.