Regulatory uncertainty and past compliance issues can exclude otherwise qualifying cryptocurrencies from approved trading lists.
Too little corroboration in the last 3 days to call a trend (2 articles). Watching for it to gain traction.
"However, that outcome remains uncertain because the SEC has only proposed the rules. Market participants will also need to assess the final eligibility, disclosure and compliance requirements before determining how widely issuers could use the framework."
"XRP, the cryptocurrency created by the founders of payments company Ripple in 2012, has been left off the approved list for now. The token would seemingly qualify given the criteria, but XRP over the years has gone through regulatory troubles—stemming from a since-settled SEC lawsuit against Ripple—that caused the token to be delisted and then relisted on several exchanges, which could be playing a factor."