Each time he scheduled a return appearance in that city, he'd send out an email letting people know the date and time of the show and a link to buy tickets.
Today, people build their followings on social networks that barely let you even post links to your own site (Instagram). Had Twitter/IG/FB existed back then, people would have no way to maintain independent contact lists.
Spam is a huge problem.
And I get it completely. Over the course of years, Google and the likes probably have more phone numbers of my contacts than I have. Only three weeks ago I made a text file with every name and number in it, so I have a safe copy for myself.
You shouldn't have to worry about suddenly losing your list of contacts. Google should be required by law to provide your data to you in cases such as account termination.