This is missing the point of interviewing. The goal isn't to find any warm body to fill the chair, the goal is to find someone qualified to do the work who also has a history of doing good work at previous employers. You also don't have unlimited headcount and hiring budget, so it's worth making the investment to find the top 10% of your applicants rather than picking first-come first-serve.
One of the things you don't realize about the hiring market until you've been reviewing resumes for a while is that problem employees are over-represented in the candidate pool. The most qualified employees spend the least time job searching because they're given offers right away. The most problematic and underqualified employees are frequently searching for jobs after being fired or let go. If you sample applicants at random, they're far more likely to be in the underqualified and/or problematic group than in the great employee group, statistically.
The other thing that isn't obvious is just how damaging a single bad hire can be to a team. Hire someone who clashes with their peers and fails to deliver any good work and you'll find yourself losing the good team members very shortly. Nobody likes working with painful coworkers.
That said: The analogy of a "walk-on" job isn't dead in tech. If you pick a company you want to work for, find someone on LinkedIn, and send them your resume with a short pitch about why you want to work there, there's a good chance they'll at least strongly consider your resume. Nobody is guaranteed a job this way, but it's one route to getting your foot in the door even when you don't see the exact job posting you want on the website.