Because, at the time, Top Rank didn't feel Cotto was built enough (as a STAR) to put him in against Hatton. They were very confident in his ability but believed they had a burgeoning star on his hand and they weren't ready to put him in the big fights yet. Don't forget, Cotto wasn't what you see today. They were slowly creating the brand, putting him in fights at MSG (NOT in front of packed houses back then).
Here's a quote from Cotto from mid-2005: “Those fights are coming,” Cotto told reporters. “A lot of people don’t realize that boxing is a business. Sometimes fights make sense and sometimes they don’t. When a fight with Mayweather makes sense, we’ll do it and it’ll be a business decision. And I’ll be more than ready.”
Here's a quote from Cotto from mid-2005: “Those fights are coming,” Cotto told reporters. “A lot of people don’t realize that boxing is a business. Sometimes fights make sense and sometimes they don’t. When a fight with Mayweather makes sense, we’ll do it and it’ll be a business decision. And I’ll be more than ready.”
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