Derek Morgan was a loner... At least, he tried to be. Anyone with a background like his would understand, people you care about are at best something you were at risk of losing, at worst something to be used against you. Unfortunately with a job like his there was no way he couldn't become close with his teammates, all he could do was make sure that they were the only people he let in, ones he could trust to take care of themselves, people who knew how to stay out of danger.
Naturally this kind of thinking put Derek's romantic life in shambles, that's not to say he wasn't successful with women, just that in order to keep them at arms length he had to move through them at a fairly steady pace. Despite the reputation this earned him and the constant reproval of his teammates, that was how Agent Morgan preferred it. He had a particular weakness for women, he knew how easily the ones he cared about could be used as weapons against him, the only way to protect these women was to leave them before they became too attached.
Unlike Hotch, Morgan wasn't a family man, he didn't see himself settling down, figured that one day, probably sooner rather than later, he wouldn't be fast enough, strong enough or smart enough and he'd die on the job. The best he could do to ensure this caused as little collatoral damage as possible was to leave the grieving to those who surrounded themselves with the gruesome. The team at the BAU were no strangers to death, they at least, could be trusted to handle his death well.
Derek Morgan, was not the type to become attached... Ever.