complete newbie to anything electricity related so would appreciate an answer I could easily understand!

I'm wondering how electric poles are placed around an area by an electricity company?
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Are they distributed across an area in a way that benefits any party in any way like saving energy, saving on poles construction or what not?

Also I'm guessing as an area progress and new buildings are built I'm sure the way the poles were initialy placed is not as optimal as it could be for the new buildings around. Is this a common practice of rearranging the poles to better fit the new changes? Does electricity companies do this often? Is it cost effective for them to find the best new "layout" to replace the poles? How does they do that if even?

Thanks in advance.