There are many reasons, but the simple idea of "containing" is a big part of it. You could run several versions of Python, database systems, etc. on a single machine, but it rapidly becomes confusing in most cases with dependency clashes, losing track of where everything is, etc. Anyone who worked on multiple projects ~20 years ago and didn't use VMs might remember how it felt.
It's like if you have a workshop and you diligently organize all of the different parts into different trays in different units so it's easier to do all the types of work you need to do. You could just have a giant box in the corner where you chuck absolutely everything.. far less complex, but it'd make your day to day work a nightmare.
It's like if you have a workshop and you diligently organize all of the different parts into different trays in different units so it's easier to do all the types of work you need to do. You could just have a giant box in the corner where you chuck absolutely everything.. far less complex, but it'd make your day to day work a nightmare.