Some games implement weather effects just for the looks and the feel, which is still nice if done properly.
Having it also affect, farming, player movement, and other thigs would be even better, but it requires a lot more development time.
I guess this could be done later on, when all other things work smoothly.
Also, a thing to note is that the more complexity with such stuff (for example, going for extreme survival elements), can also make the game "too hard" and not likable to a lot of players.
Everything needs balance.