I wonder why you bring your Instrument to a concert?
Lots of folks have a 'signature uke' like a Mahalo Smiley, and they bring it and a sharpie to the concerts for the 'meet & greet' time with the performer, and then ask the performer to sign it. Some folks have a signature uke with lots of signatures on it.
It is just but one more way to capture the memory of that day with your musical hero.
In the ukulele community as well as greater folk music world, the performers are much more accessible and open to meet fans after the show, not like if you go to see Sting, Madonna, Bruce Springsteen or the Rolling Stones, where you have to have a VIP ticket or Backstage pass for $1,000 extra, in order to spend less than 2 mins in a room with the performer, surrounded by bodyguards...
Been there, done that, was not impressed. Angry that I spent the money for nothing memorable.
I have been able to spend quality time with James Hill, Anne Janelle, Victoria Vox, Li'l Rev, Jim & Liz Beloff, Craig Chee, Sarah Maisel and others at ukulele festivals, not just in workshops, and not just watching the concert, but throughout the times when those things were NOT happening. These folks are very kind and enjoy talking with people.
Jake is likely too busy now to give workshops and schmooze with the plebs, so the 'meet & greet' thing is how fans can get close to him and have a photo or get an autograph (on their uke if so desired).