You would be wrong here. Esperanto is actively used every day, and a good amount of people use their system in Esperanto, too. You can see this because everything that permits community translation generally has people at some point starting a translation. TEJO, a youth NGO working on EU and UN level, has an office using Linŭ computers in Esperanto and software in Esperanto enables the usage of these computers by all people in the office. There are other organizations too. Also, by having an Esperanto version you often enable other minority language versions where people have difficulties learning English. This is exactly what happened with the Ipernity project, where the Czech and Chinese version were done using the Esperanto version as a pivot language. There are also about 200 - 2000 people who have Esperanto as one of their native languages. Also you have to realize that Esperanto is both easier to learn and easier to get translated than many local languages, so it does provide access even to people outside of the community.
It's hard to give an accurate number of users of software in Esperanto. I do know that many projects have teams of over 10 people translating, so the people using the translation is probably a good amount higher than that.
You are right that people often have to actively select the Esperanto version, and whenever possible I always do. It's not a statement, it's a way to get the people you need to be accessible in big non-English markets to care about your project and often help you out even for free for those languages too.