I'm surprised to see Blockstream Green and Casa on the list. Fortunately, they will both likely be deploying Bech32 address generation in the not-so-distant future. At least, that's my interpretation of
this and
this.
As for ChipMixer, I believe they have very good reasons not to implement Bech32 yet:
I've always assumed it was due to the slow network adoption of Segwit. Until a few months ago, Segwit transactions comprised significantly less than 50% of transactions on the network. Moving all of Chipmixer's activity to Segwit would have therefore compromised its anonymity set. Best to use the most common form of Bitcoin address, right?
Now that Segwit adoption is hovering in the 50-60% range, the transition is more justifiable. (To be fair, I'm not sure about the proportion of bech32 vs. wrapped P2SH usage, though.)
As it turns out, Bech32 only represents 3.5% of the network if measured by number of UTXOs, or 4.6% if measured by the number of BTC stored. From a privacy perspective, it seems reasonable for ChipMixer to continue holding off.