But, Bitcoin didn't worth the same all these years. It's a false thought to compare 2012 with 2016 and then with 2020, 2021, unless you think that one Bitcoin will worth a billion dollars when the reward shrinks by a lot. If the price isn't doubling each halving, then the security will decrease.
Besides, OP didn't refer to the previous rewards, but when there won't be a reward.
I'm not comparing anything I'm just showing the trend and those prices are reported by the time of halving. Feel free to use any average price you like to see the same exact trend.
Also if you read my following line after the dates and prices I say that this is a trend that we had
so far and there is no reason for it to change in the foreseeable future which is the next decade or two at least. What we can't predict is what will things be like after 100 years, saying anything about it is meaningless in my opinion.