I tentatively agree with the idea that conferences reduce the amount of work that someone gets done for a few days (you can see this by how much work free softw

I tentatively agree with the idea that conferences reduce the amount of work that someone gets done for a few days (you can see this by how much work free software maintainers like myself generally get done during conferences), but I absolutely disagree that it is a net negative for your employer. In my view, as someone who contributes to free software as my job (though the rest of this is somewhat related to proprietary developers too), conferences are a great opportunity to have IRL discussions over current development topics as well as meet people from other free software communities (who might work for proprietary software companies). And arguably that is getting work done (and I have written patches side-by-side with someone while at conferences quite a few times). Having connections in your field, as well as being well-known by your field (perhaps by submitting talks to conferences) is very useful for both you and your employer. In most cases, a lack of conference attendance by a company is seen as a "bad smell" in some communities (it indicates that they don't have an interest in the community around something they use -- maybe because they think that interacting with their community through conferences is a waste of time). It also potentially gives you access to more recruits, because people looking for work often attend conferences to expand their connections. Not to mention that most medium-and-larger companies can spare a few thousand dollars a few times a year to send their employees to a conference to act as both a marketing tool and as a form of training at conferences. I'd bet that medium-sized companies spend more on stationary and tea+coffee supplies yearly.