Why buy silver is an important question, but one that is easily answered.
When an economy is unstable and the financial market is uncertain people look for stability and security for their assets and, perhaps, even for their day to day trading ability.
As evidenced by recent events, relying upon a paper currency is very uncertain and the value of that currency is dependent, these days, more upon the manipulation of that currency and the debt levels that have been created in the banking industry, rather than the results of production.
Something is needed then, which a person can convert their assets and savings into that will not be subject to inflation or recessions and which will provide some hard security in the times to come. Silver is just that something and is why buying silver is so important.
There are two types of silver to buy depending upon the purpose. There is silver bullion bought as a safe haven for ones savings or assets. This could be silver in the form of bullion bars of various sizes and weights. How much one pays will depend upon the size of the bars and that will depend on the size of the assets one wants to preserve and if easy access is required perhaps at a later stage. As a general rule, the larger the bar the cheaper to buy ship and store but the harder to convert into cash at a later stage and one may not want to convert all ones silver at a time. The smaller the bar the more expensive but the easier it is to move around and easier it is to sell.
Silver that could be used for trade would best be in the form of silver rounds. That is silver coins that are manufactured by private mints and are not legal tender. These can be easily accumulated over time and stored easily and one can trade or sell any number of coins from one up to ones entire hoard if needed. These coins are commonly one ounce of silver each and easily converted into cash in the cash for an emergency or can be used as payment if cash is not otherwise generally available.
The above basically answers the question, why buy silver and, although there could, be many other reasons these, from the viewpoint of financial security, probably are the best.