It's a little difficult for Samsung to make iPads.
The same hasn't been the case for tablets because the Android manufacturers haven't made anything worth wanting. The iPad can be competed with, even if it's only on price.
Face it, if Androids selling today looked like they did in 2007 (which is to say, a lot like a Palm, Blackberry or Nokia smartphone) they would NOT be doing so well.
A quote from John Carmack comes to mind:
"Patents are usually discussed in the context of someone "stealing" an idea from the long suffering lone inventor that devoted his life to creating this one brilliant idea, blah blah blah. But in the majority of cases in software, patents effect independent invention," Carmack wrote on Slashdot, "Get a dozen sharp programmers together, give them all a hard problem to work on, and a bunch of them will come up with solutions that would probably be patentable, and be similar enough that the first programmer to file the patent could sue the others for patent infringement."
There is often one, single "best" solution to a problem. Someone else might have already done it, but what are you going to do- deliberately make your experience worse? Every phone manufacturer has borrowed at least something from another, it's the nature of the beast.
Had they stepped up and made a device that people wanted then there wouldn't be any need, but just like with the Nexus range of phones, it seems that Google needs to drag their partners kicking and screaming into making devices that customers actually want. Mind boggling.