Rivets vs Welding

I've not fully studied aircraft construction techniques so forgive me if the
answer to this is obvious. I've noted that most(if not all) aircraft made
with aluminium airframes seem to be riveted rather than welded. I'm not
sure about aircraft with composite or fibreglass skins so I won't be
dogmatic on that point, but anyway.

Is there a reason why aircraft would be riveted rather than welded together,
particularly on the airframe, not the skin? I would have imagined that
welding would produce a stronger join, although it may be harder or
impossible to disassemble if needed. Thanks,

David