(T) Remap question

Something I don't get...

A remap will (I believe):

a) improve power
b) improve fuel economy

So why doesn't the car come like that in the first place? Surely that would make sense?
Does it cause any warranty/insurance problems if you get it done?
Would a dealer say anything if they notice during a service?

far too much to say on that but its all been said before.... use the search function is my advice

In a nutshell...

The map is the same on ALL the cars with the same ECU/engine combo.
The cars are used in countries all over the world.
They must work in all sorts of environments under all sorts of conditions.

The maps are not perfect, no map is. To get a good map takes time. Also, the standard map will be conservative because of the above mentioned factors as well as a large safety margin with regards to ignition advance and fuelling. The skeleton of the map remains when mapping, it is just tweaked to be better for the conditions it is used in and in conjunction with any modifications which will allow for extra advance/fuelling at specific RPMs.

Yes you need to inform the insurance. No I wouldn't inform the dealer, it's hard for them to tell.