Capcom didn't consider Monster Hunter World for Switch, as they don't feel it fits the pick-up-and-play nature of the platform

Switch owners were quite disappointed to find out that Monster Hunter World wasn't coming to the Switch. Thankfully we're getting an exclusive title in Monster Hunter Rise, but fans of the franchise still wonder why Capcom never brought World over. In an interview with Eurogamer, Capcom's Ryōzō Tsujimoto finally explains.

To be honest not really, because we do treat each title as its own concept and you can't ignore the hardware you're releasing it on when you design the game. If you've got something like Nintendo Switch which is pick up and play, you can play it anywhere, you don't necessarily want the same gameplay experience which is designed assuming you're sitting in front of a big TV on a sofa for four hours straight. We want to be able to design a game that you can pick up for 30 minutes on the go, before bed, and get something out of that experience, and that that really affects the gameplay design and you can't just bring that over and have it be the same, so we never really considered that when it came to Monster Hunter World.

Later in the same interview, it was confirmed that Monster Hunter Rise has been in development for 4 years. That means the project kicked off before Monster Hunter World even released!