Why? Because is very sensitive, able to show trend ending without any delay, but not in the middle of it.
Being able to see such immediate trend change on higher timeframe, is a great indicator of trend direction.
Adding just security() calls to 'highest', 'lowest' and 'close' didn't seem right, because it produced some ugly , D+ and D- plotlines.
I wanted to see plotlines, which look exactly like those on actual higher timeframe. Therefore I modified the calculations.
You can read more about my take on (not) using security() calls in my other source code indicator MTF: link in comments.
On top of all that, I added interpretation of DMI readings, because it is not as simple as plus>minus + ADXrising = uptrend.
So GREEN background means higher timeframe uptrend and RED background means downtrend.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.