[pxx]

They've been mandatory since 2008. (NEC Section 406.12).

Many people don't notice they exist. You have to examine the outlet fairly closely to notice them but certainly any new construction is all TR receptacles now (with the possible exception of the ones very far off the floor).

[bombcar]

Most residences are more than fifteen years old, so people won’t notice changes. Also modern shuttered outlets are better than the first ones that were available, so you won’t even notice unless you look closely.