People who move out permanently are not avoiding paying taxes.  They do not use the services and have paid taxes all along when they did live her.
Those who go for six months certainly are not free from the Canadian tax burden.  Both aging groups free up a lot of Medical care space to the aging population still here.  The cost of health care abroad for snow birds is extremely high.  So it seems it's a win win situation for Canada. Not so sure how Mexico feels about it.  Although there is probably enough spending by the snow birds and permanent expats that it evens out.