I think it has to depend on what you are making as well. Straight lines and such, gluing seems like its easier for me but like others have mentioned, when you are needing to finesse a curved stitch line or something similar where it is nice to have some on the fly adjustments made, then not having glue is preferable.
Reading all the responses, it seems like we're not really definitively answering your question because there are too many potential things that can keep gluing all the time, or not, from being a cut and dried solution. You gotta figure out when you need to and when not to.
You said you are in the leather industry so I'm guessing you are beyond hobbyist and should likely look at bottom line as a driver in which case you need to decide where using it vs not using it makes production faster and easier or adds some robustness to the piece that stitching alone doesn't. Gluing isn't just a sewing aid, that crap (rubber cement, tanner's bond, e.g.) is strong as hell. I've torn leather trying to separate it on occasion.