The thing about tourist visa is about working in the country. That means "stealing" a job from a citizen of a country.
Nobody cares if a person during his/her holidays answer emails from his/her job in his/her native country.
From another perspective, even if there is not law saying so, for the guest country it's nice to have telecommuters. They spend money on the country, they (probably) won't use the health system (an maybe must have their own private health insurance), and they don't "consume" any of the country's jobs.
But the best part about having a telecommute job is country hopping. A big plus of switching countries at least every 179 days is that unless you are from the US or Eritrea, don't have to pay income taxes nowhere.