Most applications do far more IO than what is necessary for the task.

Anyway with a modern SSD I don't think you are right. My disk can do something like 3 GB/s and 100k random accesses per second. At that rate most desktop programs should have the binary and all dependencies loaded to memory in approximately 0.1s. That seemingly doesn't stop a lot of them from taking several seconds to boot. Likewise games, despite usually consuming less than 10 GB of video and main memory combined, can take much longer than 3.3s to load.