It's not about rights so much as responsibility. Having said that, my Meeting is now re-evaluating the extent to which it treats Members and Attenders the same. Recent appointments of attenders or unseasoned Friends to positions of responsibility have caused some tensions and problems within the meeting. But again, it makes sense to have an individual who has committed to the Society and has a certain knowledge of Friendly practice in positions of responsibility. As to why application for membership must be by letter, I suppose this makes sense from the perspective of keeping records and organisational history.
Friends are complicated and vary a lot on the approach to evangelism.
I come from a meeting which is also distrustful of evangelism. And anyone who disagrees is off to Hell. For many years I was uncomfortable with evangelism and would have resisted any proposal for active evangelism by my Meeting. However, I do believe that the time has never been better for Quaker beliefs in so much of the world. If we have found something that has value to us, that we believe will help many people, then surely we have to make that information available, to Publish the Truth.