It's probably related to the size of the company. Most of the companies I've worked for in the past have been between 50-200 employees across the entire org. The dev teams were usually around a 10-20 people and the director of R&D often encouraged us (the devs) to recommend new hires. They still had to pass through HR but it was more of a formality and the director had the proverbial majority vote.

Smaller teams are also more tight-knit so recommending a new potential dev wasn't a matter of process - it was literally head down a few doors and have a chat with the director.

I'm sure it's significantly different for huge enterprises where even the teams within the R&D department are heavily siloed.