If someone invited you to their wedding, do you have to invite them to yours?
Not at all. Weddings you’ve attended in the past should have no influence on your guest list. An invitation to your wedding means “I would like you to be at my wedding,” and you shouldn’t use it to say anything else – including “thanks for inviting me to your wedding.”
There should be no expectation of “paybacks” for wedding invitations. Things can change between weddings – relationships change and evolve, people’s locations, stages of life…People also have different wedding budgets and expectations for the atmosphere of their wedding. There is nothing wrong with declining to invite someone to your wedding just because they invited you to theirs, in fact it is wrong to do so.