STON.fi may restrict certain tokens in its user interface to protect users — for example, when a token violates safety criteria or rules used to flag suspicious activity. The exact reason can vary case by case, and we don't try to publish a static list of "why" for every individual token.
If you need to understand why a specific token has been restricted in the STON.fi interface, please contact STON.fi support. We can give you the current, accurate answer for that specific token, which is more reliable than any general explanation an article could provide.