I usually book through hotel programs preferred channels. The most compelling reason? The promotions that many hotel programs feature throughout the year.
If you watch closely and you travel frequently enough you would lose out on extraordinary opportunities if you book on third party or opaque sites.

If you look at the value proposition of the average hotel guest program without promotional time periods one might see the reason why a number prefer alternative booking channels. There simply isn’t much gold in them thar hills…….

What is the promise of an upgrade anyway in many hotels? A view when you are likely to be out of the room? A quiet room? Hopefully every room is quiet and clean. A pool view? A fax machine? At an InterContinental hotel on Priceline for 75 dollars I had free breakfast and a balcony water view high floor room a few years ago.Better then many booked direct through the so called preferred booking channels

Many upgrades are subjective and unless you are in a hostile management culture that is poisoned you can get any of these by simply asking or paying a few bucks more. Unless the hotel is sold out or unusually busy.
In fact on the rare occasions I do use Priceline or other such site I sometimes find myself more satisfied then when I pay through preferred booking channels. Hilton and Hyatt for example have never denied me an upgrade or complimentary breakfast ever as an elite member no matter how I book.A few have said ok its a one time exception or something like it.......

In fact on a Hyatt stay over this past year as a Diamond member in the former Westin Century Plaza now a Hyatt the complimentary Diamond breakfast was so skimpy a croissant and coffee that I wished I had booked on Priceline or other such site. Thankfully that was/is a rare exception. Points today are worth earning only when the program delivers and executes its benefits.If they are not doing so remember with the declining value of many point currencies they aren’t worth what they used to be so points aren't the end all they used to be.

It pays to do ones homework and be an educated program user. I used to throw my money round in the 80s & 90s on hotel whims.Today I invest my money and use my travel dollars wisely where the return is fair.
I urge you to do the same as it bests suits your needs
Cheers