Not really necessary to bet on stablecoins just to think that spending top coins is kind of a waste. Remember that in some gambling sites, there's a feature where bettors can place a bet on USD value to still control the bet on their preferred USD value while using cryptos.

But either way, I think that's not really a big deal for gamblers. If that so, we should see a declined in numbers of gamblers during the bear market but still, the crypto-gambling is alive and kicking regardless of the market trend. 

It's because gambling is gambling and crypto-gamblers will just gamble for their usual purposes. Simple as that.