The only 1 without button I have noticed is the little gate iin the historic side in the medical center area for carts only. There may be others, but have never seen any. We drive around looking at million dollar homes all the time just for fun. Bridgeport (saw a $1.3mill home with a 2800sq ft garage for sale a few weeks ago!), Pine Hills and a few other areas. Never a problem getting in or out through any gates. Most newer areas aren't even manned.
They can still take pictures (they do have devices that record pictures that move, even an iPhone can do it)
so I don't think clear photos are an issue. I think it just started out that way many years ago and they just continued the "tradition." I don't find it a "problem," it usually works fine, I just find it an unnecessary annoyance that (IMO) serves no real purpose.