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I dont think there are more (and finer grained) gems than there are libraries on, say, java or python...

For the number you can be right, but I never saw in Java (I don't know in Python) jars like this one: http://downtowncartel.com/randexp-gem/. It's a generator of random strings matching a given regexp. Take this as a general example. Let's say I need this feature in my Java project. If it's provided as a jar I need to add the dependency to the building environment (hoping that it is in the maven repo), add it to Eclipse and if the project is a command line app, be sure that the class-path is setup correctly (if you are smart and know your business you can almost automate all). If this is the granularity of a jar file I have to deal with I can soon end up with hundreds of them creating a potential maintenance headache. Personally I would think twice before doing this. Usually I prefer to copy and paste the relevant snippet of the code because it's way faster for a simple feature like this one.