I don't think it is used much in Indian restaurants/takeaways. It certainly is in Chinese ones. I love the stuff but have never added it to curry.
You can search the term "BIR" which is "British Indian Restaurant" and find lots of recipes and tricks they use, I guess ours here would be similar, I knew a guy who worked in one here and lots of stuff he said I have seen on the UK videos. There are several Chinese youtube channels doing both BIR and UK Chinese takeaway recipes. And forums too
On the Chinese ones they tend to cook it out, I have never seen it just sprinkled on at the very end on its own, though they can make a salt & chilli powder mix (salt, msg, 5 spice, chilli, maybe garlic powder too) which can be put in a salt cellar and sprinkled, but usually its sprinkled on while still cooking.
I cook a lot of BIR, I sub out half my salt in a recipe for MSG. It just gives a nice little additional oomph to the flavour. It is widely used in Japanese cooking also.