Totally agree. I think that Symfony2 is a pain in the ass.
Laravel lets you have something working really fast. Then you can improve the code later on.
Agreed, Symfony2 is great, but I see it being used more in an open source project capacity. Working on it at a company where time frames are key, rapid development is huge. Plus, laravel is far more intuitive and I can ramp up new team members much faster.
I don't see how Laravel lends itself to "rapid prototyping" than any other framework. Sure, Symfony2 or ZF2 has best practices on how to do things, but at the end of the day it's just MVC - you can skip any best practice you want to just get something done. This isn't unique to Laravel.
It's less verbose than Symfony2 and, being pretty opinionated, requires much less configuration for new applications.
Facades, macros and route closures supports rapid prototyping and are pretty easy to replace as needed. Included libraries like Flysystem, Cashier, Elixir and the new cron wrapper also eases rapid development.
There are also a few tools around it, like Homestead and Forge, that makes it easy to set something up quickly.
It's not like you can't do rapid prototyping with other frameworks, but Laravel, to me, is the first PHP framework that actively supports it while providing a flexible enough structure to grow in.
I think it tends to do with the marketing. Lots of hand-holding walk-through tutorials and help people get "rapid" prototyping with laravel, moreso than the actual code itself. And, to an extent, when you present yourself as being good for "rapid dev", that's what people will associate with the framework. (by comparison, zf has never promoted itself as allowing for rapid development, AFAIK).
I have worked with Symfony2, Zend Framework, Yii, Kohana and Laravel and find Laravel the most intuitive to work with.
I like that you can start using it for very rapid prototyping and refactor into more complicated structures as the application grows.