It is also quite common on higher end projectors to have some common inputs and then have other input options.Erm when you are paying the sorts of dollars that [user]ruinexplorer[/user] would have been paying knowing his venue, production cost is no reason to not offer an option...
My $0.02 worth, at some of the pro AV events and shows a few years ago people were talking about about HDMI likely being replaced by DisplayPort. However, DisplayPort did not rapidly displace HDMI as expected and people may still be reticent to integrate DisplayPort or Thunderbolt until related devices they are more prevalent and until there are other devices (routers, switchers, DAs, etc.) available to support them. The simple reality is that the pro AV world would probably prefer to have never had to deal with HDMI, DisplayPort or Thunderbolt, but they are what the consumer electronics world, and especially the computer industry, elected to use and we are stuck working with them.