Boss! De-CAY! De-CAY!

Remember when you used to condition yourself to clone and update your insurance every time you switched planets? Was that fun for you?

Or how about when you decided to repair your favorite blaster before a hunt with your guildies only to have the think break apart due to repair fail? Oh boy, wasn't that immersive!?

Replacing your armor on a weekly basis? That was awesome!

I personally opted to dabble in TK so I could have inherent armor, plus heal my own wounds through meditation. Because doctors were far and few between.

Well, that's not entirely true. Some were on kill/resurrect macros in the Village so they could achieve Jedi-hood. Yoda would be proud.

The concept of minding ones gear isn't a bad one on paper. It adds a level of complexity to a game system, plus it is a familiar concept from the real world that can be translated to a game in such a way that the idea makes sense. "Oh my pistol is damaged, I should fix it!" as opposed to "Negative Jawa Faction. Huh?"
SOE did not handle the decay system well enough. Degradation happened too quickly, had the risk of permanency, no guarantee for incremental fix success and could potentially be too costly.

With the old 'mix-and-match profession' system of yesteryear, a player could decide to dabble in the crafting professions in order to better their chances at maintaining their gear. The Combat Upgrade virtually removed the dabbling for those who wanted maximum combat capabilities. The NGE officially removed it.
Under the new system, players would resort to using crafter alts to maintain their gear on their combat character. So what's the point? There are those who wouldn't rely on alts, but they would find themselves robbed and crunched of their credits in order to maintain their gear.

All on the assumption that the gear could be maintained without risk of it exploding into uselessness.

And also assuming that the rate of decay doesn't become the main focus of combat. The threat of dying shouldn't be built upon the fear of losing a favorite shirt, nor should the downtime between combat be centered around finding a way to repair the damaged gear.

Repairs and maintenance are a part of the Star Wars movie lore. Just think of Han, Leia and Chewie all messing around with the Falcon. Artoo and the droids fixing the Queen's shuttle. Or even Luke with his X-Wing on Dagobah. How about the Rebels outfitting their snowspeeders for the cold? It's there, so it does have a legitimate place.

But SOE failed. The system left a bad taste in everyone's mouth. No good came of the system, and its return would add nothing to the game to improve playability, immersiveness or fun. Crafters continue to sell their goods, despite the lack of decay. Show me a crafter who cannot make a profit and I'll show you a crafter who should find the profession counselor and seek employment elsewhere.

SWG does not need decay again. Once again, it seems appropriate to say: "If it ain't broke, don't fix it."