Check out this map.
For one thing, did you know you could drive from Dubai to Ras Al Khaimah without passing through Sharjah? That's because Dubai is not a connected set. Neither is Sharjah, Ajman, RAK, or Fujairah. You can even drive straight from Ajman to Fujairah.
I recall reading that the British deployed the Trucial Scouts to determine the present day borders of the seven emirates. And that they did it by surveying locals to determine their allegiances. I suppose the idea was to set borders that would be politically stable.