So what's stopping them for doing this? Pumping up new game and new IPs should the priority for them.
Nintendo generally refuses to buy studios because lets be honest most of the Industry doesn't want to work for Nintendo so if Nintendo buys them likely lose most of the staff rendering the buy useless.
Until Nintendo expands its genres and starts making things outside their comfort zone they are not going to be able to woo a lot of developers to stick around in new purchases.
The Industry thrives on disloyalty to studios. Developers etc. jump ship all the time and Nintendo operates in its own world where such concept is foreign.