Travellers who are able to live on legal sites do pay council tax towards local services on the same basis as other people.

The assumption that tax evasion is greater any other section of the population is just that, an assumption. If that kind of argument were being made about say, Jews in general, it would be recognised for what it is.

People who get out of paying their share towards the common good ought to be made to pay, fair enough. And most of that does in fact involve wealthy people with dodgy lawyers, and it's called "tax avoidance" rather than "tax evasion" and it escapes prosecution because it's so complicated and expensive prosecuting the people carrying out the scams that they get away with it.