Too Long; Didn't Read
Web apps are anything but simple these days and since they have to work under the limitations of all the slow components, the CPU ends up making up for it. Even basic apps with all of their trackers, external javascript scripts and doms take up 100s of MBs in memory. Native apps use the GPU a lot more efficiently, they can recycle items and do a much better job at hardware acceleration via the GPU. The web has the advantage of easy accessibility, but we have sacrificed too much in terms of user experience.