When I am asked or permitted to share in a meeting, I’m discharging a duty. The duty is not personalised, even though the content is.
Accordingly, I’m not doing the meeting a personal favour by sharing. I’m not acting out of generosity, as I’m duty bound to proceed, and declining would be a dereliction of duty. The answer to the invitation, thus, is ‘yes’ not ‘sure’, in the same way that a good employee says ‘yes’ not ‘sure’, as though they might just as well have declined.
The meeting is also not doing me a personal favour. The meeting is not there to bestow individualised gifts but to achieve a common goal, with all of us contributing to achieve the common goal. The meeting is not being generous by asking me; it’s merely performing its function. The answer to the invitation, thus, is ‘yes’ not ‘thank you’.