Good morning Hari
One the reason is cost. If you are not aware, TVCs are predominantly produced by FMCG companies for food, hairwash, bodywash, icecream, shavers, handwash, detergents.
You will notice the TVC that is produced is region specific and used in the countries in that region. Most models for hairwash are from Thailand and the voiceover language is then dubbed accordingly for a particular country.
I recalled a TVC on Singapore TV on Lifebuoy handwash using India Indian kids and found it strange for use in Singapore. In any event, I don't use Lifebuoy as I find it extremely "toxic" on my hands. I prefer Kirei Kerei which is much better.
I doubt any FMCG MNC would want to incur specific costs for specific country TVCs.