As an ex sandwich artist, now sandwich artiste (I quit and do it at home for myself now):
I STARTED putting normal amounts of mayo. My owner was 1st Gen Chinese and frugal as fuck so she drove that into us "1 line, half if they ask for light, 2 line if say more" were her exact words
Sooooooooooo many people said "more. No, more" that we all started defaulting to more when someone asked
Even if you dont ask for it! One time I just got done ordering my sandwich, they grab the mayo bottle and say "you want mayo?" Then jizz out half the bottle all over it before I can say no.