Why no bolt together slides?

Long time follower of DIY firearmery - long enough that I used to exchange emails with Phil Luty back right around 20 years ago, and I don’t care if y’all believe me or not.

That means I’ve been around since Phil, Loompanics, and Paladin Press’s offerings scanned into JPEGs and so on, as our generation’s equivalent of STLs being kicked around… which means the major designs were subguns for simplicity.

With that focus on rudimentary and FA fire came the associated illegality worldwide, and the lack of decentralized collaboration which helps drive development today. I’ve been able to watch a small scale Industrial Revolution kick into hyperdrive over the last 25 years, or more realistically, the last decade.

But here is a question which surprises me. What is putting designers off finding ways to slides? In the same way you don’t have to print a lower today or even weld one up, and could find something commercially available in the 80% products out there if you wanna - plenty of people prefer to build as much as they can.

So why does it take some Swedish guy playing at Lego with some PRC equivalents to Send Cut Send to put these things together? Images all from Impro Guns, I haven’t been able to find pics of anything similar elsewhere.