I can tell you with certainty that this is not a universal practice
In some jurisdictions profits earned on currency exchange operations are not taxable, and its official. Further, if Bitcoin is treated like property (or property rights), you may look for tax exemption. Again, in many jurisdictions if you held some property for longer than one year (in some parts of the world longer than three years on expensive items like houses or apartments), you don't have to pay a capital gains tax. Technically, you still have to pay it but you receive a tax deduction which equals the price at which you sold this property, so effectively you don't pay this tax
I don't need that. My tax service officially declared that they have nothing to do with Bitcoin
In some jurisdictions profits earned on currency exchange operations are not taxable, and its official. Further, if Bitcoin is treated like property (or property rights), you may look for tax exemption. Again, in many jurisdictions if you held some property for longer than one year (in some parts of the world longer than three years on expensive items like houses or apartments), you don't have to pay a capital gains tax. Technically, you still have to pay it but you receive a tax deduction which equals the price at which you sold this property, so effectively you don't pay this tax
If you have been selling Bitcoin and haven't reported anything to the tax agency I would suggest consulting a tax attorney or something before landing yourself in hot water
I don't need that. My tax service officially declared that they have nothing to do with Bitcoin
Which jurisdictions are that? Bitcoin is not regulated here but I found out that it is taxable because they added an addendum to the tax law for Bitcoin particularly and that change wasn't officially declared either.
Currency exchange operations are not taxed in Russia
And this is not some theoretical "knowledge". I habitually buy and sell US dollars via my regular bank account. This is basically the same "buy low sell high" scheme, though I mostly hedge again possible currency devaluation. And the capital gains thus earned are not taxed. If I'm not mistaken, there is a special provision in the laws regulating currency exchange operations which stipulates that buying (selling) currency on a given day higher (lower) than the official exchange rate set by the Central Bank of Russia for that day basically frees it from taxation (which is almost always the case). Regarding Bitcoin specifically, I posted a link to the official letter of the Russian Tax Service as of November 2016 where they make it extremely clear that they consider Bitcoin as a sort of foreign currency and as such it is not their business altogether
1btc in these countries its like 110.000 
