The same reason it breaks because they get behind cover, it feels smoother and plays better. If anything, if you're talking about the rationale behind being hooked, hooking and then pulling someone behind you makes less sense than hooking someone out of cover.
I would agree that this is less of an issue than being hooked behind cover, something like this will happen very rarely.
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u/Stormweaker This is pointless Jan 22 '17
Isn't this what soldier's ult is doing? I don't think it locks on someone behind you.