A lot of fans think a fumble through the end zone shouldn’t be a touchback. They think the ball should be placed at the spot of the fumble. I disagree. You shouldn’t be rewarded for fumbling.
But it's not rewarding someone for fumbling, it's just that you got lucky and avoided a turnover. Just like if your own guy recovers your fumble, you're not "rewarded" for fumbling. It's just that the completion of the play worked out.
What if a guy fumbles out of bounds at the five? Should that be a touchback? At the 50? Out of the end zone is the same thing. You got lucky and it went out of bounds. Still your ball at the spot it went out (or at the 1 if it went out of the end zone).
Giving the opposing team the ball just because it went out of the end zone is like rewarding the defense for
not making a play.