system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: During the PS1 era, one of the upsides the N64 had that the PS1 didn't was that cartridges had no loading times as opposed to CD's which had more capacity but had to load all the data. Why do now the cartridges on the Switch, for example, have to make use of loading screens?
gpt
Back then, the ROM storage on the cart was about as fast as the RAM in the console. So there wasn't really a need to load data, because it was already readily accessible by the CPU.

Since then CPU and RAM speeds have increased significantly. The speed of permanent storage has also increased a lot, but not by as much. Modern flash based carts are much faster than an optical disc or mechanical hard drive, but they're still significantly slower than RAM. So Switch games need to load data from the cart to the RAM in order to use it.

I suspect for some games ported to the Switch from other consoles the loading times are really bad because they have been optimised for the other consoles. PS4/Xbox One in comparison to the Switch have much more CPU power, but slower storage devices. 

So for them it makes sense to compress data because then there's less data to read from the hard disk, therefore faster loading times. The decompression won't increase the loading times because it can do that while it's reading the next bit of data. So as long as the CPU is fast enough that it can decompress at at least the same speed it can read it from the hard disk, load times will be improved.

If you port that game to Switch you might have a problem. Now the CPU isn't fast enough to decompress the data at the same rate its reading it, so that decompression might hold up reading the raw data from the cart. Maybe they try not compressing the data. That might improve load times, but those carts have a much, much smaller capacity than a PS4/XB1 game can use so it will be a struggle to get the game to fit. You face the choice of having to cut bits out of the game, reduce texture quality further, or have slower load times.