License Plate Hiragana Characters

I love finding out things about living in Japan.  I don't drive here, but I do notice cars and license plates.  Only Japan uses hiragana on license plates (see 3. kana text above). The following are never used on license plates:

1) Any hiragana with ten-ten voicing marks on the side (such as が (ga), じ (ji), ど (do) etc.)
2) Combination hiragana sounds (such as きゃ (kya), ちょ (cho), みゅ (myu) etc.)
3) Old hiragana not used anymore (such a ゐ (wi) and ゑ (we) etc.)
4) わ (wa) and れ (re) are only used on rental cars. 

In addition to these, there are four more that are not allowed to be used on the car plates:

1) お (o). This one isn’t used because of its similarity to the hiragana あ (a). During a high-speed chase, the last thing police want to do is have to squint and try to deduce if they’re tailing an お or an あ only to get it wrong. This might also be why the similar-looking わ and れ are both only used for rental cars too.
2) し (shi). し isn’t used because it’s pronounced the same as the word 死 (“death”), making it an unlucky hiragana to have. Those who have studied Japanese know that the number four (also pronounced the same) is considered an unlucky number, similar to 13 in the West. But still, there are plenty of license plates with 13 in Western countries, and their owners haven’t all faced untimely deaths… probably.

3) ん (n). This one kind of makes sense, seeing as ん is the only hiragana that is just a consonant and not a consonant followed by a vowel. There are no words in Japanese that start with ん making it difficult to pronounce on its own. When department store clerks announce over the loudspeaker that a car has its lights on in the parking lot, they want to be able to get that info out clearly, not stumble over pronunciation errors.
4) へ (he). And here we have the strangest exclusion of them all. The reason you’ll never see a へ on a license plate? Because it sounds the same as 屁 (“fart”). We assume that policemen and store clerks would just burst into a fit of non-stop giggling if they had to read a license plate with へ on it, which led to its banning. Although perhaps the even funnier image is a room full of policy-makers deciding which hiragana are okay to use on license plates actually discussing the fact that へ makes them think of farts and striking it down because of that. 

Source: soranews24.com