What's interesting about Indian units is that when you convert parsec into crore light seconds, the calculation, taking leap years into account, gives 1 light year = 31557600 light seconds and as one parsec is equal to 3.26156 light years, we have one parsec = 1029.27 crore light seconds, which is generally rounded to 1000, which is very practical.
When the place value system was created independently, the West followed a bottom to top approach while the Indians followed a top to bottom approach.
So when the French wanted to count beyond the hundreds, mille was invented. But Indians wanted to count down from 10^22 seconds, which is 100 Brahma years (311.04 trillion years). So counting down in the hundreds was far easier than in the thousands because it was done mentally. I guess this also had to do with paper being expensive compared to the Renaissance period. Similarly, it was easier to estimate the value of small objects like atoms. In Indian texts number went down to around 10^-7 seconds when calculating time. Buddha estimated the size of a carbon atom as 4x7^-10 cm via a poem, and he turned out to be right.
So when you measure in the hundreds, it is easier to calculate two digit numbers mentally, you get more divisions, and the number patterns our brain likes come in more frequently, like 1000 crore light seconds versus a very small two-digit 10 billion or the very massive 10,000 million.
Physically and mentally too, it's easier to say/think 1 lakh versus one hundred thousand. It's even more easy in our own languages; ek lakh, das lakh, ek karod.
That's why mathematicians and scientists prefer using the Indian system in India, and that's the system we teach the kids in too.
Of course, we had the thousands system too. This is from a book from 300-1000 BC.
eka (1),
daśa (10),
mesochi (100),
sahasra (1,000),
ayuta (10,000),
niyuta (100,000),
prayuta (1,000,000),
arbuda (10,000,000),
nyarbuda (100,000,000),
saguran (1,000,000,000),
madhya (10,000,000,000),
anta (100,000,000,000),
parârdha (1,000,000,000,000).
But what we use today is from Ramayana.
Laksa is lakh and koti is crore. And from 10^9 to 10^18, we use different variants of crores, like lakh crore and crore crore.
So who knows? Someday when long distance space travel becomes frequent, our standardized place value system will become part of the metric system while light years and parsec will become something akin to the imperial system.