I have no problem with this.

It's part of the deal as an employee -- there are employee perks but at time the company asks that you take a back seat to customers when you are not the focus of the event or activity. This has occurred to me attending events at the companies I've worked for where we end up with an oversubscription of attendees and they ask some employees to hold back or skip the event to ensure customers are fully able to attend. No different than asking a non-rev not to come into the SkyClub because they are oversubscribed at the moment.

This is no different IMO

I assume employees traveling on company business have some sort of T&E coverage too (likely some sort of a per diem) so it's not as if they won't be able to purchase food / beverages / etc., they just won't be able to sit in the lounge