One of the tricks with comics, though, is that everybody hates new characters. So if you want a gay character who actually matters to anything, you have to take an old character and make them have been gay all along. It's not generally very easy to believably do this, since most major characters have had significant relationships of a heterosexual nature.
Todd was one of the few good prospects; he'd had relationships with women, but they were awkward, fail-y, and he never seemed able to connect properly. These are common traits of attempted straight relationships by gays who aren't out to themselves, and any queer fan or ally with any real familiarity with that phenomenon, reading Todd's stories, might very well come away from them with the impression that he's gay and in denial, regardless of the original intent of the authors (which I assume had more to do with his sketchy childhood). It was therefore plausible that he might come out, and is therefore a coherent and sensible story that he has.
It's a bit of a balance, though, since it does sort of imply that his sexuality is linked to his childhood, given that his early behavior could be symptomatic of either and has been taken in canon to be symptomatic of both at various different times. I think the tradeoff is well worth it, we need a fuckton more gay superheroes in the Big Two and I'll cope with some barely-there unfortunate implications or the reappropriation of other stories for nefarious gay agenda purposes if that's what it takes. Others, obviously, are less sanguine.