Why are guys petty texters?

I've been texting this guy and I always find that when I leave him on seen, the next time I text him, he leaves me on seen. Once, we were texting back and forth promptly, but I went to wash off my face and prep for bed. This took me fifteen minutes. I replied to his text after fifteen minutes and he waited fifteen minutes to text me back !!??? Why is he this way? Why are men so petty? ( please don't take this as sexist, just lighthearted. I don't mean to offend anyone)