They will probably have certain contractual obligations regarding dwell times in the main terminal building for the shops and restaurants to extract maximum cash from passengers before they go out to the satellite buildings. Privately operated airports like T5 are massive shopping malls, the planes are an afterthought.

I assume you talk about terminal 5. I'm not a fan departing from 5B or 5C but in most cases that's announced at least 20 min before boarding and you can easily make it there in 5-10 min (most of which is spent waiting for the train). I experienced twice that the announcement came a bit later but then they kept the gate open later to ensure everyone makes it.