The thing that makes me notice more and do things like this is because I do it all. I've been on jobs doing data cabling but have also then done all the electrical alterations, fire alarm, security, fitted the staff kitchen, plumbed and tiled it etc... Because I do all this I know that as an electrician I will be moving the floor boxes at some point, and that I would need the data to be long enough to reach as it can;t be unplugged and moved and as I am also the data installer I can do this. A lot of data cablers or indeed any other trade specific tradesmen, just think of their bit of the job, not the job as a whole.