Maybe because there's not much they can do.

"Asia's four biggest economies all saw significant currency gains," wrote W Pesek about China, India, Japan and South Korea. "What's peculiar, though, is the lack of panic." Despite a 13% rise in the won Bank of Korea raised "short-term interest rates for the first time since 2011", on 30 November. Although China, India and Japan are unlikely to follow suit "tolerance in China and India of last year's roughly 6% currency gains -- and Japan's of a nearly 4% advance -- is reason to be optimistic". Or maybe they are unable to weaken their currencies due to other reasons. Japan introduced a negative interest rate of minus 0.1% in 2016 and has been maintaining it since. This is to discourage savings and encourage spending which will increase demand and inflate retail inflation to 2%. A negative interest rate also discourages investment funds from buying into Japanese bonds, which would strengthen the yen. After reaching a peak of 79 to the dollar the in 2012 the yen was around 116 in 2016. Today it is trading at around 108 to the dollar, although it has hardened a little bit in the last few days because of the weakness of the dollar. As for China, it is protecting the yuan to reassure its own citizens and stop them from moving money abroad. It restricted currency exchange to $50,000 per person per year. The government relaxed some controls on the renminbi last September. It is not just the currency. The government brought in stringent restrictions on selling stocks when the market collapsed in January 2015. The Chinese market was giving 50% returns last year which makes it very tempting to scamsters. So, what about the Indian rupee? From 1:1 against the dollar in 1947 it collapsed to 69 against the dollar in August 2013, during, what came to be known as, 'taper tantrum'. It is presently trading at 64 to the dollar. It is not surprising that the rupee keeps dropping in value as the rate of inflation in India is consistently much higher than in the US. Which means that the purchasing power parity of the rupee is dropping continuously. Successive governments in India have tolerated a high inflation rate because it reduces their borrowing costs and increases indirect tax collections. At 7.3%, yields on the benchmark 10 year government bonds signal the bond market's expectation of inflation. It is a warning to the government to keep the fiscal deficit under control. The US economy is doing very well yet money continues to pour into India with foreign investors buying over Rs 2 trillion of Indian securities. Our foreign exchange reserves have jumped to $414.78 billion because the Reserve Bank keeps on buying dollars to keep the rupee rise under control. Perhaps it is not that Asian central banks have suddenly become adventurous. Perhaps, at daily currency transactions at over $5 trillion, they are a bit helpless.