Commodore Remix

Why do famous musicians tend to tape up their keyboard brand names to the audience?

For example, Whilst watching Jean Michel Jarre Live in Solidarnosc DVD, I noticed that Jarre had the Brand names on the keyboards taped up. I wonder why a decision was made to do this? Jarre is well known for stating what keyboards he uses on his albums and I'm sure non musicians wouldn't really be bothered that Jarre was playing a Microkorg. People interested in synths could probably spot what synth it was anyway.

I always thought it was so they didnt give free advertising to the synth maker.

A high profile artist like Jean Michel Jarre would certainly drive up sales of any particular keyboard by displaying the name.

Someone looking up to the synth god, would want to go out and buy the same brand/model maybe wanting to sound like him.

I think its a way of saying, we were not sponsored by said synth maker.

It's more often like that: They have endorsement deals with specific keyboard brands that involve various advertising duties for the artist (doing photoshoots for ads, testimonials for their webpage etc.). They're often not allowed to officially appear with equipment by other manufacturers. But since any artist still likes to use various stuff and don't wanna handicap himself they tape up the brand name.
Same goes for guitarists (endorsed brand used for posing and videos, different brand used for recording the album) or even shoes of soccer players with taped up stripes.

One thing might be that X would not sponsor the gear, so they can't get any free exposure.

Another thing could be that if you want to sell a concert to a TV network, some networks will not show it if there are any visible brands or logos in it, because they want to sell TV commercials. It's easier to put tape on the brand names and logos than blurring it in a post process.