Well when you buy real assets someone is selling and they are left with inflating cash they need to spend on something.
If someone is investing in productive assets (companies, rentable property) for their sustained revenue potential that isn't a bad thing. Spending on goods and services will add demand to the economy and money will circulate.
There is also more reason to borrow in an inflating economy which adds money and demand to the economy. Obviously borrowing can get too high and needs moderation if bubbles are to be avoided but gentle adjustment is needed to prevent massive swings in aggregate demand.
Also I'm not arguing for high inflation just that even a couple of percent deflation could be really bad.
Isn't there some circular logic at play when you say that deflation would cause people to simply hold onto cash rather than invest in productive enterprises. Because if nobody invests in productive assets, then there will be no more goods entering the economy, therefore there will be no deflation of the currency to worry about in the first place...
There are very low incentives to investing when the markets are shrinking, and even less to employ people. Now, tell me why lower rates are usually considered a good thing for business?
Savings rates might well go negative though.
Steve Keen as linked to is well worth a read rather than my first approximation guesses.