A lot of reasons. A few being I don't like to enter promos/ask for free stuff unless it's a company I'm already buying products from regularly, or unless it's a product I would be buying/sampling/willing to pay for regardless of any promo.
Outside of a few Xtend sample tubs(which I enjoyed), I've never purchased anything from Scivation, so I would feel strange just randomly accepting free supps from you guys. I'd rather my support happen organically.
Another reason is I don't use joint support atm, and I haven't researched which one I would be buying if I did, and I'm not in the habit of just pumping supps into my body or stocking up on massive amounts of supps that I may not even use or need.
For ex. PES offered to send me a replacement tub of WCM after a shipping issue, but the issue ended up getting resolved, and I emailed them letting them know I wouldn't be needing that tub which I didn't have to do. 1 tub of that flavour is plenty. If I don't need it or won't use it, product I enjoy or not, then I'm not going to accept it just because it's free, that's a bit too greedy for me personally.
I did enter in the PES joint promo contest, but that was after some internal debate after which I decided it's PES and promo or not, I would be most likely buying it just to try it regardless.
Nothing personal at all, I'm sure the product will be top notch.