There is a simple reason: scarcity of talent. Talent that can be commoditized through a platform instantly becomes cheaper, with employers much more easily able to sift through inventory (candidates) and look for deals or just waste peoples’ time gathering market data on interview performance.

If you’re sincerely highly talented, you’re not going to advertise yourself as a commodity on a platform. Your increased skill may not have a chance to be displayed because the platform uses foolish things like coding trivia or a black box proprietary method for recommending salary ranges for candidates like you, or offers automatic ways to find similar candidates so that if employers don’t like your salary demands, they can use your characteristics to tailor a search for a cheaper version of you.

Putting yourself on a platform like TripleByte essentially instantly signals that you’re on the cheap, commodity end of the spectrum (and yes employers think of $130k as cheap salary for this type of position).

Using TripleByte is like cheapening your personal brand. In fact it’s even worse because you’re voluntarily doing it and voluntarily centralizing all of this interview performance data and profile data for them.

Everything I've read indicates that you do still have to do the normal in-person technical interview gauntlet at each individual company. It's possible things have changed recently, though.