ECU remaps. Are they worth it? Is there a discernible difference in performance?

Hi. I have a 2013 Mondeo 2.0 140 and have read a lot of stuff about remaps. It seems they improve performance and fuel consumption. If true, why aren't Ford selling their cars with ECUs already programmed this way? What am I missing? I'm looking at a Bluefin DIY kit, but before I drop on something I don't really need, I wondered if anyone had any useful pointers, thoughts or ideas. Cheers!

"true, why aren't Ford selling their cars with ECUs already programmed this way?"

Emissions standards and warranty claims mainly

Not much to gain on a factory stock engine.