The user who you replied to said that not everyone takes it meaning that there simply aren't contactless terminals out there everywhere. Walmart for instance has resisted heavily. But moreover, I think part of the issue is simply because retailers in the US aren't used to having the credit card terminal out in the open for users to interact with.
Anywhere that accepts contactless cards will also accept Apple Pay in the US. I think when users say they use card, it means EMV or mag swipe still. Contactless cards just never took off in the US. I remember around the 2008 recession or so, many cards started transitioning, but then when it never took off, card issuers started giving non contactless cards again. It took until the whole Target breach in 2013 along with Apple Pay being introduced to bring contactless cards back. Only in the last 2-3 years or so have card issuers gone back to contactless as default and I saw a few cards being replaced to explicitly offer contactless.
As I mentioned earlier, part of the problem is most retailers keep their credit card machines behind the counter and aren't accustomed to holding it up or putting it on the counter in front of the customer. So even if they have contactless support, it's a hassle and they're more used to you handing them your card in the US.
With the pandemic though, I do see more stores prominently putting Square readers out there in front so you can use contactless, so this is a positive change.