That's more a statement on Adobe's quality of engineering than computing. CC is awful software and I hope their engineers are embarrassed by its deployment for the fantastic platform that is their creative tooling.
I would argue that it’s because of vast resources.
Both Adobe’s, and their customers.
At a certain level, when a graphic designer complains that Photoshop is too slow, they don’t push back against Adobe for optimizing poorly, they just buy a new computer.
Most software surprises me with how much time it needs to start. Games are particularly slow, I guess because they need to load the entire engine and all assets before they can even show you a game menu, but even very simple applications can be slow.
On the laptop I'm typing this on, Windows Explorer often takes several seconds to open.
Games tend to be optimized for framerates so it makes sense to sacrifice load times for that. Of course there are plenty of games that are just badly optimized and could improve both framerates and load times.
Games on old machines also used to have loading screens, remember? They actually sometimes took quite a bit longer than, say, starting PS on a modern machine. I don't think games a very useful comparison in this context, it's more about utility and application software.
