As folk have already mentioned, the carriage is useful for joinery, especially tenonning. At my old work, we did a fair few bridle joints, which a carriage like that would be ideal for as you can do both the tenon and the "mortice" on it, the mortice being open ended of course.
The Yanks would do such things with a dado stack on their table saw, but the saws we have here tend not to have the length on the arbor for such things, which is where a piece of kit like this comes in handy.
Looking at the picture though, I don't see a fence which would be good to have if you plan to do such operations on it. I'm sure you'd find a workaround, but you can't beat a dedicated fitted fence if you're working on thin sections like rails or stiles.