Some Uniswap V3 stats:
ETH/USD (USDC, DAI, USDT) vol share: 70+%
ETH/USDC vol share: 50%
Stablecoin vol share: ~5%
Interestingly, most of ETH/USD vol is made through 0.05% fee pools.
So far, the biggest driver for liquidity are farming incentives. There are incentives to LP DPI on Uniswap, and AAVE on Balancer. Sushi is providing rewards for most of DeFi pairs via Perpetual mining & Onsen. The only outlier is MKR, which operates on Uniswap organically.
This analysis doesn't include BTC/BTC pairs. But, as a side note, @CurveFinance broke ATH yesterday on WBTC/renBTC pair volume: over $200 millions were traded in a single day. Pretty cool.
Looking into @Uniswap, we can see again that most of BTC volume went from WBTC pair, and that BTC pairs exploded in 2021, driving $1.5B of volume each month on Uni alone.
BTC/ETH is a huge piece of DEX trading. Just last month alone, over $4.5 billion was traded across 3 pairs (WBTC, renBTC, TBTC).
Since january 2020, over $12 billion went through BTC/ETH markets, with over 97% of that being WBTC/ETH pair.