Rate discrimination?

I’ve been a PLT for about a year now and travel extensively in the US, some 75 nights in the last 6 months alone. I often stay a full week at certain repeating properties amongst shorter stays at others.

I’ve only been upgraded to a Jr. Suite or a great view once in all this time. I also often arrive Sunday nights to a dead hotel but rarely receive a pleasant surprise than a concierge floor upgrade and often that takes asking for.

I’m wondering if my corporately negotiated rate has anything to do with it. It can take a “normally” $289+/night room rate and knock it down to $139 or lower.

Would this be a factor in determining if an upgrade is given? I’m not the loud, demanding and expecting type at the desk but always wonder how these selections are made. More often than not, it seems like the room number is “pre-blocked” already well before I arrive and it becomes an effort to change it.

Thanks for any insight.