You can be a greatest musician in the world but unless your instrument is in tune no one is going to book you more than once. However, if you spend half your set tuning up, no one will enjoy your performance either.
Audiences don’t mind if you have to tune up in the middle of your set, but they expect you to be in tune at the beginning of your set. I find it very difficult to re-tune a guitar while talking to an audience. I once broke a string on stage and then spent about 10 minutes tuning up only to discover than I had put a G string on the 4th string which meant that the guitar was impossible to tune up.