You can become a Supporting Member.
Two potential reasons:
There is a big problem in China with contracted (outsourced) factories and employees producing extra and selling those through improper channels. The company owner doesn't get paid it is reasonable they wouldn't want to warranty the merchandise. It's not necessarily fake (but may not meet standards, could be QC rejects, etc) but it isn't officially "real" either.
Also sometimes companies try to price things differently in different markets. The merchandise intended for the Chinese market may have lower margin than what is intended for say the US market. These items are considered "grey market" goods. The cost of providing warranty service in the US is likely higher, so here too may be a valid reason. (Of course collecting higher profits could be the reason as well).