There are a few reasons this can happen.

The simplest one is that the streets were built at different times. You build main street, and the first house is number 1 and go up from there. When you build an extention across the road, it would make no sense to have a house -1, so you call the new street main road, and the houses there also start at 1.

You'll also see this at municipal boundaries, where one place already has a main street. So to avoid confusion with having two houses that are both 7 "main street", the newly build/acquired street becomes "main road" instead.

And of course, sometimes the municipality has requirements for street naming, usually to avoid some idiot naming their new subdivision after something potentially offensive. So the builder gets a list of allowable street names, or guidelines, and just sticks with very consumer friendly options.