There is a very simple reason: We live on one earth, and this is the only place we can live right now.

原因很简单：我们生活地球上，而且这是目前我们唯一可以居住的地方。

youdao

The reason is simple, lions eat cattle, and as the Numbers of people grow, the Numbers of cows increase. Alongside that there are ever more efficient ways, including poisoning, to kill lions.

原因很简单，随着这里的居民越来越多，牛的数量也增多，而狮子要吃牛，人们于是采取更厉害的办法，包括对狮子下毒，杀死它们。

youdao

The reason your household is hectic in the morning is simple: There are timetables to be followed like getting to school and work on time and children are notorious for their dawdling.

大清早一阵忙活的原因很简单：你要遵守时刻表，比如将孩子准时送到学校，自己要准时上班。 但是孩子就爱磨磨蹭蹭。

youdao

The simple reason is that there is this scenario prevailing now, what we witnessed in 2008 when Lehman Brothers went bust.

VOA: standard.2010.05.17

There is a simple reason for such a harsh judgment.

CENTERFORSECURITYPOLICY: Center for Security Policy | ��The Limitation Of Nuclear Materials As A Means Of Controlling Armaments��

He says there is a simple reason for his success.

BBC: New and improved Forlan to test Liverpool

The reason is simple: There's too much wine out there to let the juice alone find its price.

FORBES: What Holds the Juice Can Be What Sells It