Actually...they did. Not intentionally, of course. But it was there from the start:
"For I have been informed concerning you that there are quarrels among you. That each one of you is saying, "I am of Paul", "I of Apollos", "I of Cephas", "I of Christ"."
1 Cor 1:11-12 (abbrv)
The Apostles didn’t start denominations.