Who is actually using an assigned license

No, there is none. And even if there would be, everybody opens from time to time a PDF document and that would trigger Acrobat use, but would not trigger specific use of capabilities above Acrobat Reader. Either you know the needs of your users or not. Managers should evaluate from time to time their team needs, that's more effective than asking for obscure logging. That works also with other things like additional hardware.