It's not the autograph that people really want when they go to a convention. It's the eye-contact, and feeling like you've commanded at least a sliver of that person's time where they acknowledge you as a human being and an admirer of their work. If they come across as robotic and fake autograph-factories, it's not exactly a great experience.
Unfortunately, the cons have become a machine, an industry. It was already getting bad in the 80s when I used to go, but it clearly is 10x worse now.
But what I remember most fondly at the conventions were off-the-cuff moments of unscripted interpersonal contact. Majel Barrett spent a long time sitting at a booth, not specifically signing autographs, just sitting there talking to anyone who cared to chat. That stuff matters. These days the stars charge for everything and it feels like hiring a very short-term escort. And this is after paying a big sum just for the base ticket, mind-you. There is all this double and triple-dipping.
This isn't specifically Star Trek, but I thought I'd mention this.
The last convention experience I had was in the late 90s and Michelle Yeoh was there. This was right before Tomorrow Never Dies came out and she was really looking to break-through into the US market. She had a long Q&A session and after that she just stood up and came around to the front and hung out with people in a very informal way. There were guys throwing their arms around her, treating her like she was their girlfriend, and she was a real trooper. Not a single dirty-look or "Um, could you call security?" vibe. I asked her to sign her name in Chinese and she did that for me. I don't know if she's done any appearances like that since then, but I'll always remember how accessible she made herself, much moreso than a typical Trek star who would stay back-stage after their talk and only show up at the end to sign.