The point is to be an official inhabitant in your town. It gives you some legitimacy in front of officials. I use it to open banks accounts, to renew my driving licence, to report my address at the immigration (TM30), to attend the villagers meeting and vote on infrastructure matters, to pay Thai entry fare in the national park of my province, etc.. And many were happy to have it in August last year when only residents were allowed to enter Thailand. Beside you get a lifelong ID number you can use on official documents instead of the passport number that changes every 10 years.
And if your wife agrees, you can be listed as the head of the household as well.
All countries that are member of the U.N. accept the IDP. It's not whether they accept it, it's whether their laws REQUEST it or not to drive on their roads. Many legally accept national licenses if it's in a language they understand (ie. I can drive in the US and Canada with my French license and no IDP). In case of accident, the insurances will just look if you comply with local laws before paying for the damages. If the local law doesn't make an IDP mandatory, you're fine with the insurances if you don't get one.
Getting an IDP is definitely not a report to your home country authorities that you intend to drive abroad and has no legal impact at home.
It's the host country that requests for an IDP while driving on their roads. Your native country doesn't authorize anything, they just provide you with the document as per the international road transportation agreement.
An IDP is nothing more than a copy of a national driving license with translation in several languages. It should be used together with the national license. If you ride a scoot with a car license, of course the police will give you a fine.