I think it is as simple as them being expected to be complicit in advertising a product they don't agree with (Ronaldo has been openly critical of sugary soft drinks and Pogba is a Muslim and doesn't drink or want to endorse a beer company). Growing up in the early noughties, no player would've...
So I guess the flag shaggers were right - these footballers are a bunch of capitalism-hating Marxists...
In all seriousness, I think it is remarkable how footballers no longer tow the line. Long may it continue.