For me the main reasons for using a package (particularly one as well used as spatie's) are:
- why re-invent the wheel
- you can access a lot of help (as lots of other people are using it)
- its well tested/developed (again as lots of people are using it)
The big disadvantage (from my POV - as I'm still very much in the learning phase with Laravel and php) is that if said package doesn't quite do what you want - it can be difficult tweak.
I guess everything is a trade off, you don't have to use packages for anything - you dont even need to use laravel.