Something funny is happening in my native Belgium. Some people drop their fifth formal working day to become bicycle couriers, Uber drivers or whatnot in the "sharing economy". The reason is taxation regimes.
80% or 100% gross wage as a median income employee will hardly make any difference in net wage around there. A friend for example recently got a promotion from an entry level job (with tax discounts) to something more in line with her qualifications (without tax discounts). 600€ gross salary increase translated to 155€ net salary increase. All the rest got eaten by tax and social contributions increases.
Belgium combines high formal job taxes combine with a low tax scheme meant to formalise "sharing economy" jobs. These enjoy super low 10% taxation up to 500€ per month. Many people actually do the math. They switch to 80% formal jobs hardly losing any income. Some actually increase their income by becoming pizza couriers or Uber drivers in their 20% time...
UPDATED: corrected the net wage delta from 100 to 155€.