Why does not samsung release their exynos source on the internet?

Why does not samsung release their exynos source on the internet? or release a flashable aosp rom or something like that rather than making a new phone with different number and has aosp just like they used to do in the past (Google play edition) why don't they just release an aosp rom and you can flash it yourself? xiaomi did it not with aosp but with windows 10 they released a flashable windows 10 rom
if i am paying $700 for the device i should have full control of it
i am going to get HTC 10 since it has SD820 and it's UI is similar to stock anyway

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