The downside is that your code doesn't optimize for free. iOS is over 50% of the mobile browser share in the US and desktop Safari is 11-12% (roughly 1 in 9) a

The downside is that your code doesn't optimize for free. iOS is over 50% of the mobile browser share in the US and desktop Safari is 11-12% (roughly 1 in 9) and both implement proper tail calls and have for around 6 years now. Despite this, the world has not collapsed and people aren't constantly complaining that websites are constantly breaking.