[mostlystatic]

Maybe I'm being overly literal, but do some people just receive offer letters without going through an interview process?

Sure, I get lots of recruiter emails, but almost all of them are sent identically to 100 other people as well.

Most emails I get come from external recruitment firms, only sometimes does someone at a company reach out to me directly. But even then it's only an invitation to apply, it doesn't mean I'm actually especially likely to get the job.

[briandear]

I got a no-interview, no resume offer for a contracting gig simply off the basis that my LinkedIn showed that I worked at "reputable company." I couldn't believe it -- but the contract worked out and everyone was happy. Social proof often means more than a resume or even Github.

[nfriedly]

It happened to me recently, the offer was from someone I had previously worked with who just knew and trusted me.

(I also get about 1-2 recruiter spams a week and occasionally one that seems genuinely tailored to me specifically. This might be what the OP was calling "offers".)

[fleitz]

Yes. I was taking my wife out to dinner once and a recruiter stopped us (me) in the street to get me to work for their company, technically I interviewed but it's kinda just a formality when they want you that badly. Apparently a former co-worker said I was a genius.

As others have mentioned, it's social proof.