Doing TCP from a "native" JS app should be pretty easy[1] (caveat: I haven't tried.) I'd think the cost of running a proxy server would be enough motivation to figure this out, for any developer whose primary reason is as simple as technical difficulties with JS and TCP. I think it more likely the other responses such as doing heavy indexing that won't work as nicely on the clients.

[1] https://stackoverflow.com/questions/41674063/is-it-possible-...