Why does it need to be written when feelings could be simply understood?

Feelings or emotions are personal.

No two persons can feel the same way even if they are blood relatives or born twins.

There will always be a change in how people view and perceive the situations, others and their reality.

However, when it comes to feelings, nowadays in the 21st century, let's say that people are more inclined to express their feelings in the written form along with verbal and facial expressions.

For example, when two people are in true love, they are more willing to keep expressing their love every now and then in written and verbal format more than understanding the care, affection, love, respect and all positive emotions on their own.

Why is it so that people want written proof of their feelings of each other when it has to be felt from within and not just read or spoken about simply?