Well as Adibordoy said its down to banks, and can always swap to Google Pay and use it across all your Google devices even if it's not Samsung specifically. Like I use Sony phone as well and via Google pay it automatically syncs across without any issues.
As other users have already mentioned (thanks!), the number of banks available on Samsung Pay depends on the banks themselves, not on the Samsung. Therefore, unfortunately, at the moment, nothing can be done regarding your suggestion 😕.