In short because not knowing something really bugs people.
We humans tend to be inquisitive by nature. So, we developed science in order to satisfy our curiosity and to understand the natural world.
The whole point of science is to try to understand the natural world around us. We do this through repeatable, statistical and empirical means in order to try to figure things out, and try do so with minimal error.
One of the big things that are bugging scientist today is: where does life come from? Obviously we see life all around us, so it must’ve come from somewhere.
So the current running theory is that life is just very complex chemistry. And for life to have started,(as it obviously did), it needed to self replicate, and the two well-known molecules that can self replicate is DNA and RNA, but further testing needs to be done in order to figure out which molecule came first.
It may not end up being DNA or RNA at all, but some other nucleic acid we have yet to discover. That’s what makes science so cool, because it’s on the cutting edge between knowledge and ignorance.
I hope that helps.
