I was reading back then on bsn that one of the devs confirmed it was to avoid people scolding each other if one doing worse than the other. It was a quite few years ago so cant look for which post it was but if they had years to make it possible but they didnt, then probably there's a good reason why not.
Also if we look at the majority of the MP games, almost every of them have some chat interface, and even smaller companies with less budget could make it possible so i doubt time or the budget were the issues that were preventing it to happen.
Might be wrong though, but its my opinion.
While normally I would agree with you, in this case I went with my "gut". It's happened before with Gears of War, where you had to use the console to chat online. A few other titles have also followed suit in recent times, mainly when involving console ports.
Any kind of obnoxious chat you don't want to see / deal with is also easily fixed. It's called being able to mute/block a user. Blizzard does it with Overwatch fantastically and they have have a presence on both console and PC. Voice chat in that game is opt in, or can be set up in the menu to be opt in, which I only occasionally do on competitive mode. If people start typing rude tings in chat, it's REALLY easy. You right click their name, click "Mute", "Block". and/or "Report". Muting simply makes it so you can no longer see any text chat from them. Blocking prevents friend requests and future game matches with that person. Reporting is obvious. :-)
If Blizzard can do it, Bioware can do it. any "toxicity" issues are merely excuses. All it takes is a little time and effort to give the PC user base a bone we've asking to be thrown our way for some time.
