That is the point of my reply, you can consider the marketed "no-KYC" swap service a scam if they do not have any written form that mentioned that they may require KYC data on certain transactions.
In principle I do agree with you, but in practice I do not. We could basically call almost all marketing a scam, even the largest companies in the world at least partially lying with their marketing. For example, they tend to cheat a lot with benchmarking phones or processors in unrealistic setups and then advertise their products with false data. If a swap service does not require KYC in 99.99% of the transactions, what should it write instead? "Almost never KYC?"

Like I said, write something like "
they may require KYC data on certain transactions." in their TOS, even as small as one phrase.
They can advertise "
no KYC" as shameless way as possible, but at least mention the above and they could get out of the "
scam exchange" category.
In case the user didn't read the terms of using the service, they can call it his fault.
Alright, we are in agreement with this. It should be noted in the TOS and they can advertise as no KYC as this is about the same level of marketing lies that most companies engage in. I will use ChangeNow as an example to check it again for the purpose of this discussion.
3. AML/KYC Procedure
3.1. The Users don’t need to create accounts: you don’t need to register or log in to use the Website. However, ChangeNOW uses an automated risk management system to check all the transactions made by the Users.
3.2. By accepting these Terms you agree to pass through the AML/KYC procedure, which may be applied to you or may be requested by ChangeNOW at any time.
3.3. During the AML/KYC procedure, ChangeNOW reserves the right to request additional information and documents, including but not limited to scan of your ID document valid in your country and additional information of the funds' origin.
3.4. In limited cases (such as to verify your identity in order to pass the AML/KYC procedure), we reserve the right to freeze your exchange transaction for any period of time necessary to complete the investigation and AML/KYC procedure.
While the investigation is ongoing, ChangeNOW reserves the right to transfer the frozen funds to a cold storage. It would be done for ensuring their safekeeping.
3.5. If you deny to pass through the AML/KYC procedure or don’t provide ChangeNOW with the requested documents and information, ChangeNOW has the right to refuse to execute your transactions (current and future).
3.6. By accepting these Terms, you agree and warrant to provide true, accurate, current and complete information about yourself and take full responsibility for its accuracy, completeness and veracity.
3.7. For more information, read the official ChangeNOW's Rules of Anti-Money Laundering and Combating The Financing Terrorism Compliance Control here.
3.8. Starting June 2021, ChangeNOW works with a KYC provider called SumSub.
3.8.1. If a User’s exchange has been stopped for a KYC check due to an alert from ChangeNOW’s risk-management system, ChangeNOW provides the User with a link where they can pass the verification procedure in a safe and secure manner.
3.8.2. The verification time window is 3 days, and the User can refuse to pass the procedure; in that case, the User will be provided with a refund.
In limited cases (if the transaction is suspected of being connected to illegal activities) we reserve the right to freeze your exchange transaction for any period of time necessary to complete AML/KYC procedure and all relevant investigations. In such case we may refund the transaction upon the request provided by the relevant authorized bodies.
https://changenow.io/terms-of-use/changenow-termsIs it perfect? Absolutely not. However, actually their TOS is not that long and this is near the top of the whole page. This confirms my statement that it is primarily:
1) User laziness.
2) Refusal to accept responsibility for the consequences of your own actions. If you did not read the TOS and something unexpected goes wrong (but which is part of the TOS),
it is your fault and only your fault.