Lifetime Platinum Marriott member here.
The special treatment is OK. It is nice to get room upgrades and freebies, but that's little stuff. It doesn't get you a room magically when they are sold out, and you don't magically get a better rate when prices are high.
The biggest benefit if you're traveling a lot is your points accrual rate is higher with status, which lets you more rapidly exchange points for things. The only sane way to spend points of course, is more hotel stays. Nothing else comes close value-wise. I recall running the numbers on that (points/dollar ratio), and you'd be a brazen fool to spend points on merchandise - when you compare the ratio of hotel stays to merchandise point cost, you realize that they have a 3-4x markup on the merchandise.
That's when you spend your points. Though it depends severely on the brand. Marriott and Hilton are no longer great. But Wyndham and Hyatt are pretty amazing. Starwood, used to be good until Marriott bought them out.
I have never found this to be true unfortunately. I have some conference related travel coming up, and the conference made some deal with Hilton for a special rate. Hilton's link wouldn't work, and I made 5 calls trying to get them to offer a discounted rate to no avail. Eventually had to book at a discounted rate on hotwire (same as the conference's rate), which presumably made Hilton 20-30% less. At scale, hotels are just operated like commodities. Unless you are really special (loyal and big spender), you won't get any special treatment.