Thomas Stanley and William Danko wrote 'The Millionaire Next Door'. In their research they profiled people who typically get rich:
Place far more emphasis on saving than consuming
Live below their means
Typically self-employed and run a small business
Not flashy
Industrious disciplined conservative
Make money because they are very good at what they do
Productivity and passion for work is the common denominator. The money merely arises from their efforts. Their focus is not to pile up money, it is to run their business well.
As to millionaires on this forum, there are probably far more than you suspect, millionaire being defined as one who has more than $1,000,000 in investable assets.
In my country, interest income is fully taxable, so investing a million in government bonds will give an after-tax income that is close to the poverty line, not to mention that inflation will erode the purchasing power of that million and the annual income it can deliver without risk.
If you are rich and want to stay rich you have to accept risks - or keep working.