I don't think Gravatar is an obstacle to creating an account (It doesn't block or stop you in anyway). But I assume you mean that once you have created an account you sort of have to go somewhere else to then set your profile image (provided you didn't have one already).
Plenty of people have an issue with Gravatar (or any third party site) on SO so you're not alone:
Obviously the reason they went for it was that it offloads the storage of images (which may have been more important back when the site started), it's an existing solution which people were already using and in a way is actually very handy for sites that support it. Another use is that Gravatar also has default images for when accounts don't exist or change which is much better than seeing the "missing image" on the site (which will no doubt occur if users host there own images) as well as providing a simple API for scaling which is pretty neat.
It seems fairly reasonable that at some point they will either host profile images themselves, allow an image URL to be specified or integrate imgur in the same way the post editor now provides a simple way of uploading photos.