From my experience, developers often feel pressured to achieve a lot of work in a very short period of time, possibly using technology that they are not so familiar with, in order to build a “Proof of Concept” of something. I have experienced this myself several times. The rest of the company are having fun being creative and “brainstorming” stuff, making presentations, while developers are stressed out in order to finish coding something before end-of-day presentation.
My suggestion is that developers know in advance what they will work on so that they can make sure that the scope is within reason. It also allows them to get started right away in the morning, without needing to wait around for a project to surface. Also, don’t force someone to come up with an idea themselves.