Just to add here, I have to agree with you!
REAL physical money (hard cash) is also used by criminals, WAY even more so than crypto, per $...
...and in terms of resource use / harmful fossil fuel use - normal physical currency (coin minting, cleaning, transporting back and forth, destroying, re-creating, not to mention banknotes, creating, cleaning, destroying etc) - the process for NORMAL currency to be created, and actually used, stored, transported etc ALL uses 'harmful fossil fuel' energy (or worse!) in some form.
I really don't like hearing one-sided arguments, so felt the need to balance this up.
Having said that, to answer your original post - It would be cool, but I still feel that 99% of crypto is WAY too volatile to purchase stuff *without* having the vendor change it to a stable coin once paid in, unless they have a REALLY good feeling about that market, but in terms of @WTF's point about the ecology, I have to disagree, in your favour.
Some people seem terrified of what Crypto can be (ab!)used for, but the fact is that institutions have been able to monitor, dictate, tax, syphon funds, and generally abuse the existing financial markets (and customers), blow BILLIONS on known bad deals / transactions, yet award themselves 100's of millions in bonuses, and track everything *YOU* do, by linking your account, personal details, etc, and following card purchases, payments etc.
This level of monitoring and control is beyond any legitimately required, so it's no surprise that lots of people are embracing the anonymity that crypto transactions and crypto markets in general provide, for completely legitimate reasons.
TL;DR ....So yes, I think crypto currencies ARE the future (if the governments of the world, and banking/financial institutions aren't allowed to outlaw it somehow - and even then.. ;) ), but sadly at present I'd say that it's too volatile to use for everyday purchases - like others also mentioned, the GOOD thing about is is that it generally changes price more rapidly (making it desirable for shorter term investments, vs. historical markets), but then people don't want to spend it if they think it will rise, and don't want to sell it at a loss - it's difficult to justify purchasing stuff with it, rather than exchanging or trading it for other stable coins or crypto... I refer you to that original Bitcoin Pizza purchase.... :)