Why do electrical ladders have linear drains?

In today’s time almost every shopping mall, airport or similar places have electric stairs installed, through which humans avoid spending energy on climbing or descending stairs, but have you ever wondered why there are long linear drains on these electric stairs?

Although these lines add to the beauty of these stairs, the real reason for creating them is not to create beauty in the stairs. You may have noticed that at the beginning of these stairs a comb-like metal is also installed, which cleanses any kind of garbage that comes with the shoe or the grid that goes into these drains, due to which these stairs are not even stuck.

Also, if any solution that causes slippery falls on the stairs, it also goes directly into these drains.and does not cause slippery to people, while the comb installed at the beginning of stair cleanses it.