Comment by da_chicken

I think it's tied to the fact that many developers are given unreasonably capable systems (compared to end users) for running their software, or else exclusively test on small data sets or without considering resource limitations or real-world situations.

I've seen plenty of product demos that work fine with test data, but once you introduce real world things like: 200+ concurrent users that need to do more than just navigate to the 3 most easily demonstrated screens; application is hosted at a data center in another state; making that hosted system be a shared tenant; introducing data of real-world complexity; making the client system be a system spec'ed for a basic office worker 5 years ago; installing web filtering and other applications and not only running your one application.

Suddenly, loading N,000 records into a dynamic gridview table on a page load becomes a real bad idea, and the occasional needing to view logs or audit trails that reach N,000,000 records to load into that same dynamic gridview table means the site just times out.

It's a similar reason why you can sometimes find that you have to scroll right and left on a site. Well, that's because the dev has multiple 32-inch monitors in 4k or 8k, and they're not designing the interface for the 1080p laptop screen that most of their userbase actually has.