I am 100% in favor of the more turnout the better, but the blanket statement that they will just get used to it just doesn’t apply to every horse. One of mine loves to live out and the other has done himself serious injury more than once (for example: torn RF suspensory, bone bruise on his ankle, and then an injury eventually requiring hock surgery) because he wanted to not be outside and/or his TO situation wasn’t exactly perfect. He HATES bugs, but hurls himself to the ground if you put on a fly mask, cannot be turned out or even share a fence line with other horses or he will attack them or play so roughly it amounts to the same thing. And so on.
I’ve never had such a diva about turnout ever and it’s a huge PITA! He used to refuse to wear a flysheet but luckily he now consents to not throw himself on the ground. Still no fly mask. He has a scar on his face from my last attempt.

My point is that everyone’s situation is different and some of us are just doing the best we can with a suboptimal boarding situation or ridiculous horses who are super high maintenance. My barn puts them out as much as possible, and several horses are on 24/7 TO, but everyone knows that if they see Steve throwing a tantrum out in his little field to bring him in or the next step is probably going to be calling the vet. 