In the grand scheme of menswear, the emergence of sporting separates can be viewed as an act of liberation away from the staid and traditional tendencies of men to don a two-piece or three-piece suit in strict unison. The world is becoming less formal, of course. While the sartorial rules of old continue to shape our generic approach to tailoring, you'd be a dinosaur to think that they couldn't and shouldn't be tweaked with at the least. Separates exist in a dynamic middle ground and are the perfect mode of personal expression, as they require the wearer to shrug off uniformity. Today's approach to separates perhaps owes something to a certain cabal of financiers who, after the crash of 2007-8 had willingly subscribed to the standard uniform of navy and grey suiting in a bid to gain financial stability, suddenly needed to up their game as central banks printed unprecedented levels of cash. Not wanting to revert back to their Monday to Thursday get-up as they were reaping the Bernanke put, but still desirous of a certain level of formality with a jacket, they opted for a sartorial pick 'n' mix with chinos, tailored flannels or denim. Overall, the emergence of separate tailoring was simply a natural evolution, the same way that sneakers have transgressed from their sporting roots and into fashionable domains.
The reason why one should consider breaking up suits is that it allows you to be versatile in your choice of ensemble and that it presents you with the ready-available option to be expressive and creative. It is, though, a hurdle that many men drastically crash and fall at. This is because there are guidelines and basic rules to follow if one wants to achieve an understanding of a casual sense of elegance.
First things first, there are four fundamental elements that need consideration: fabric, tone, pattern and fit, all of which are just as important as the other.