I know I broke the law on the way back from the station earlier as I did 61mph in a 60 zone. Just because I didn't get caught doesn't make it legal.
Defacto, going 61mph in a 60 is legal practically everywhere. De jure, it's not (the law is on the books).
Same as jaywalking. It's more of a law to pass responsibility in an accident (i.e. if you were jaywalking and got hit by a motor vehicle - you are at fault because of jaywalking. Jaywalking itself is very rarely prosecuted as a standalone thing)
They obviously can't prohibit people from checking emails or taking work calls while on vacation, because that means the end of big-spending tourists.
Nobody has drawn a red line at a magic point along the continuum from one emergency work call during a two-week holiday, to 9 hours a day in a hotel room hunched over a computer. Where would it be, and why does that particular point maximize benefit for the host country?
And your statement is nonsense, murdering someone is illegal whether it's proven or not.