The original reasons for not putting your elbows on the table (limited space, as well as some others) just don't apply anymore. There's no reason _not_ to put your elbows on the table other than "that's how it's always been done". As such, at least in my opinion, the rule no longer applies.

Until you do it on a temporary table and knock over everyone's drinks

sailors eat with their elbows on the table, to keep their fare from sliding as the boat rocks. don't look poor!