The elephant in the room is that the liquidity and trading on BitMEX is legit and many times higher than spot, yet BitMEX is unregulated. Big players can and has used BitMEX to manipulate spot prices (arbitrage/market maker bots will move the price on regulated spot exchanges accordingly). It used to be that most of the manipulation happens on Okcoin futures products. Since the China fiasco in 2016-2017 they lost almost of all of their traders to BitMEX.
Those exchanges that don't submit data are either doing shady stuff, or don't care to be listed (which is perfectly fine).
"5/ Only 10 exchanges have >$1M real daily bitcoin trade volume. @binance, @bitfinex, @krakenfx, @Bitstamp, @coinbase, @bitFlyerUSA, @Gemini, @itBit, @BittrexExchange, @Poloniex / @circlepay You can see the daily BTC trade volume on these exchanges at: http://www.bitcointradevolume.com "
Note: Not verified by me, just relevant to the source.
[Now I'm going to peek at the actual volume rankings. Hmm, not bad - Kraken is doing better than I thought, and I underweighted Bitfinex and Bitflyer per U.S. bias, but it's otherwise quite close.]
https://coinmarketcap.com/rankings/exchanges/
I think it's pretty well known within the crypto community that CoinMarketCap exchange volumes are bullshit - other than Binance, the top 45 basically consist of exchanges I've never heard of. They're bullshit because there is a ranking, one that many newbies would refer to, and it's trivially easy to fake volumes through wash trading or just lying if you own an exchange. It's been like that for at least a couple years too - when I first found CoinMarketCap, the top exchange was BitMEX by a large margin, which everybody said to stay away with and doesn't even appear today.