why do you degas wine but not beer?

In wine making, degassing unbinds the CO2 from proteins making it easier for the wine to clear completely after fermentation. I actually find the same is true of beer. After secondary fermentation, I use a vacuum pump to degas the beer and it's usually clear within 24 hours. Yes, I end up re-carbonating either in the bottle or keg. Some people accomplish the same thing with cider by using bentonite to bind to the proteins after fermentation.

What I have learned is that yeast when first pitched needs oxygen to grow strong and multiply, that is why it's best to introduce oxygen either by oxygen tank setup or agitation of the wort before pitching the yeast. The co2 gas emitted during the first few days of fermentation would be detrimental to health and vigor of the yeast and that is why during the first few days degassing the wort is essential for a good fermentation. .

The purpose of degassing in wine or mead is to benefit the yeast. CO2 is toxic to yeast and inhibits the yeast's ability to fully ferment the larger amount of sugars in wine/mead.

Degassing mead is highly recommended during primary fermentation to help the yeast, even if you plan on making a sparkling mead.

I'm curious about whether beer would benefit from degassing, though I suspect that yeast can handle the levels of sugar typically found in beer without needing to have CO2 removed from beer.

Wine is degassed because it is served still. "Still" is a term that means not-carbonated.

Beer is carbonated, so there is no need to bother, since you are introducing CO2 to the beer anyway. Mind you, there are phases of beer production on certain styles where you are essentially degassing, (diacetyl rest) but that is for different reasons than why you degas wine.

As to mead, that depends. My mead is sparkling, so I don't bother degassing it. If your mead is going to be still, then you would need to degas it.

Hope that helps.

I don't make wine, but my understanding is that the purpose of degassing is to release the remnant CO2 still in solution at the completion of fermentation. CO2, of course, is desirable in beer, so one wouldn't want to expel that after fermentation. It's the opposite with wine.