If you're primarily interested in getting a job, and can cold email a company and get an instant onsite, then going for that is a totally valid option. The most time-efficient way to get job offers is to get introduced to hiring managers (self-intro if necessary), make a good impression on them, and ask them to jump you along in their firms' hiring practices. I've said that here for years; I'll continue saying it.

There exist many engineers in the world who either a) cannot cold email $DESIRABLE_SOFTWARE_COMPANY and be guaranteed of an interview, b) do not believe they can cold email $DESIRABLE_SOFTWARE_COMPANY and be guaranteed of an interview, or c) are not comfortable executing on the process of emailing $DESIRABLE_SOFTWARE_COMPANY and getting an interview. Those are three subtly different problems. We are a partial way to address them, and other problems besides.

a) A very talented engineer might not have a resume/background/etc which pings the radar very hard at a software company. If you do, great, more power to you. Try to put yourself in the shoes of someone without a great educational pedigree whose last couple of jobs look something like "IT at insurance company. Responsibilities: rebooting printers." or "Network administrator: CISCO routers, light systems administration." That person might also be able to black-box cryptosystems, find RCEs in Rails given a day of effort, or program trading algorithms, but the company won't find that out because they likely won't even be offered a phone screen.

b) You know how impostor syndrome is a thing? Oh boy, do a lot of very talented engineers have it. If you can program, many desirable companies like e.g. Stripe would love to make your acquaintance. If they don't offer you a job they will not feel like talking to you was a waste of time. There are a lot of people who do not get this and benefit from being told some variant of "I understand that you feel like you've still got lots to learn. I've got lots to learn! And I've been doing this for 12 years! But I see from your demonstrable performance that you're actually good at this. The folks at Stripe trust my judgment about this -- if I'm making a mistake about this, well, that's on me and not on you. Why don't you have a call with $PERSON there? I predict that they are super-inviting wonderful people who will want to geek out with you about tech stuff; if a job offer happens after that, wonderful. But I can almost guarantee you that no job offer happens without you talking to them."

c) Many engineers are afraid of selling themselves, for personal reasons/cultural reasons/etc which our community unfortunately frequently amplifies. Even if you tell them "All you need to do to get a job is a) meet a hiring manager, b) convince them you're not an axe murderer, c) get a coffee date and do your thing, d) say yes to the job offer", they're not willing to take the clearly valuable first step of sending an unsolicited email. I am totally willing to send a (very) solicited email on one's behalf, if I feel like a candidate and a client could have a productive conversation together. I'm also pretty good about writing that email.

Also: for the right kind of person, the challenges are fun, in the same way that chess or poker or Starcraft or sudoku are fun. Except with more REST API.