Modify or add functionality according to your needs
The functioning of every company is built on unique processes (a furniture company uses a different set of processes than a law firm). And the more the system can do, the greater the chance it will not be able to do it in a way the company needs.
The best fit for these unique needs would be a custom-made system, but custom development is very time-consuming (depending on the complexity of the system, from months to years) and very expensive (for medium-sized systems, on the order of millions).
For time and financial reasons, the most advantageous choice is often a compromise - a ready-made general system, most often in the form of a rental.