Could lack of speech be due to a hearing problem?

Absolutely it could. That's one of the common causes. It could be many things. So definitely if your child is having issues with speech or hearing get it checked.
But you actually have time before you have to be really worried about your 2 year old. Sometimes kiddos take a little longer, and its not a major concern until... 4 I think. I hope someone else corrects that if I am wrong.

I think it depends on the amount of delay Jennie.

If the child doesn't have any speech at all by the age of 2, I'd definitely worry about hearing problems, and I'd get it checked right away. The sooner you know what's going on the sooner you can get help for the issue.

Now, if your child has some speech, but not up to par with other 2 year olds, then I would wait and see.

It's never a bad idea to get help with any issues. The younger these kids are seen, the younger they are when issues are diagnosed, the better off they are in the long run.

I wish I hadn't waited until my son was 4 to get him assessed. If I had gone when he was 2 he would have had an extra 2 years of help before starting school. As it was, he had only 1 year, and because of that he was still delayed, and needed an aid and speech therapy until grade 4.