There is no economic importance from robbery if anything it's the complete opposite. It causes higher prices which are then past on to the consumer.
What is the economic importance of robbery?
Robbery can sometimes be seen as an economic indicator of how an economy, or a section of society is faring financially and socially.
There are theories that suggest the more financial pressure a population is under, the higher you can expect the crime rate to be. Especially for crimes that are motivated by financial gain, such as robbery.
However, economics is rarely that clean cut, and there are of course many factors that can impact crime rate.
Everything from availability of contraception through to the purity of street heroin can influence crime rates indirectly, within a time period.
And associating robbery rates to poverty or economic hardship doesn't always add up.
For example, after the financial crisis in 2009, the FBI reported incidents of crimes such as murder and robbery actually fell across the board.
There's an interesting article about the link between crime and poverty here if you'd like to dig deeper:
http://www.newrepublic.com/article/80316/relationship-poverty-crime-rates-economic-conditions
I don't think robbery is important. We'd be better off without it