The big problem is definitely the security needed these days; as Weeters said, it was interesting in 1994 when the worst folks you ever encountered usually posted their manifestos via the mail and everyone self-policed themselves. But once Columbine and 9/11 happened along with the Internet, stalkers, then just general distrust of mainstream media setting in, you had to block out those folks from getting on camera as a threat to the safety of others, so now outside set parts of the day you're looking at an empty window outside the Today studio where unless you brought the right sign or sob story to get in for a game or makeover on the 4th hour (or now, well pre-vetted ahead of time), there's no way you're appearing on-camera.
It's why the concept has just completely died locally outside of controlled weather decks and balconies; those stations just don't have the budget to provide security that NBC has, along with any idiot ready to yell 'FHRITP' and attack the talent. Who would want that headache?
Add to that the pointless 1515 move that still stuck CBS in a windowless studio and ABC eventually retreating to the safety of the second floor, because pedestrianization of Times Square now means you have to deal with multiple headaches outside the Naked Cowboy, the cavalcade of unlicensed characters and the 'unwashed masses', which especially after Tony Dokoupil's interview with Ta-Nehisi Coates...yeah, you'd be questioned deeply if you wanted to send him and Gayle out to do a cooking segment on the Square.
It's also so damned bright now with all the signage and is probably a nightmare to light/shoot around because ad screens are on 24/7 rather than just still images lit only at night (my trip to Times Square last year was on a drab and rainy day and it felt like that block was lit like 30 car lots), so that was another reason CBS had to cover the windows and ABC's only Times Square shot is now just that one generic shot of the big screen. All of that is a reason TRL is no longer a thing too; it used to be you tolerated Limp Bizkit to get to see Britney Spears, but today's music 'stans' will try to derail a free event with an artist they hate in any way they can (and the reason for the hate is probably very banal).
Finally, most people are there just to get a picture with the talent, so once you get it...well, you're done. It's not 1998 any longer where it'll take a bit to get that picture from the lab. You got your TikTok/Instagram moment. Instant gratification. Why stick around? Outside the concert series, who wants to stand around watching a morning show backwards through a window you probably can't even see through, probably through loudspeakers which sound awful, and an outdoor uncovered plaza subject to rain, snow or cold? You'd be better off waiting for winter to get facetime on the skating rink wide shot or under the tree, where you know you won't get hassled by regular cops and side-hustle security guards.