Not necessarily. Unions can and do negotiate terms that protect union members to ridiculous extents at the cost of making what is basically an underclass out of non-union employees and employees of other unions. You'll find terms that limit certain scopes of work exclusively to employees of a certain union, and even employees of that union with a certain standing within it. Some of this work is gravy train shit that you'll never get to see if you're not in the union or not in the right union. In some unions, working non-union jobs can result in repeating fees for the length of time you do it. Do it long enough and you'll be so far in the hole that you'll effectively never be able to pay it back, you'll never be in good standing, and you'll join the rest of the employees outside of your union that can't draw crazy high pay for very easy work.