I don't believe practice is the issue.I don't think that's how it usually works in practice though.
The issue (from what we've seen in many threads in the past) is that many people believe that races should have set ability modifier bonuses as that is the way of defining races. Goliaths are bigger and stronger than other races, so they need to have that +2 STR to denote that (for example). But if the game removes these modifiers (or allows a player to put their +2/+1 into any stat they want), then they are removing an important facet of racial distinction.
But my argument is that Player Characters are not in any way representative of the average people of any races, specifically because they can be completely opposite of what the average member would be. You're right in that we might not (or rarely) see a player make a Goliath PC with a STR 12 or a Halfling PC of STR 15... but that doesn't change the fact that we can see them as per the rules. We can have weak Goliaths relative to other races in a party... so that so-called "required" +2 STR needed in the racial write-up (that some people suggest needs to be there) to be emblematic of the strength and size of Goliaths relative to other races is completely lost. The game didn't need to give the Goliath a +2 STR to represent the race's size and strength, because the player themself completely negated it when they decided to play a Goliath with a strength of 12.
If we players can negate the "average" person from a specific race by how we place our scores... why are we forcing the book's racial write-ups to attempt to do it? And thus why I think this is why they are removing the +2/+1 ASI from races and putting them over into Backgrounds.