The first line in that Bloomberg article sums up everything pretty nice, no need to read it all...
If you want to buy Bitcoin without actually buying Bitcoin

The same way you can buy gold and when the times comes you realize that you can't make even an engagement ring from the ten kilos of paper gold you have in your safe.
And a second paragraph made me really laugh:
Unlike exchange-traded funds, ETNs are debt instruments that are backed by their issuers -- often a bank -- rather than a pool of assets and often focus on esoteric strategies that dont easily fit in a fund.
That definitely convinced me to go all.....the way to the right corner and close that page

Who writes this stuff?