I mean. What did you expect him to do?

I had some contractors that helped extend my lanai. At the end, I bought everyone a nice lunch, beers etc..

Its a way of showing thanks. Genuinely, what would you have rather they done?

That's a client, not your employer, they already pay for the service you provide and in their case the company has control over how much they charge for it.

What we're talking about is your boss taking part of the money that client pays and buying pizza for the staff instead of giving them proper wage.