The initial project at Hive Helsinki, libft was an opportunity to learn many fundamental things about C such as string manipulation and memory management. The school projects are set up so that you are only allowed to use a very limited selection of library functions, so that's why we need to create our own. It was a very good exercise and made us think what really happens "under the hood" at all times.
The library acts as an utility belt during the later projects and I have expanded on it with my own functions that I felt would be generally useful. I will most likely keep expanding it for a while still, at least as long as we'll keep working with C.
One part of the expansion of the library is also that I've merged a few other school projects in it, such as ft_printf and get_next_line.