Why do we need four Plone add-ons with almost the same functionality?

As part of a new project I am looking into the fullcalendar integration with Plone.

There are currently four different modules available for Plone which basically provide the same functionality:

• zettwerk.fullcalendar
• Solgema.fullcalendar
• ftw.fullcalendar
• collective.js.fullcalendar

I could not find any major difference among those modules - neither functionality differences nor visual differences.

Why the hell do we need four packages?

Every company seems to have enough resources reinventing the wheels on its own?

Do I have to waste my time as an integrator for checking four packages myself.

Why can't you guys work on one package supporting fullcalendar?

Being slightly pissed of with too many options basically doing the same...