They must have their own reasons to think or say like that about Bitcoin. Their business is not based on Bitcoin, nor they have any investments in Bitcoin, so they get nothing nor they lost anything by saying something good or bad about Bitcoin to anyone, so the better is not to listen what they say. But to be honest, maybe what they say is not totally senseless, since Bitcoin is just a digital currency, though it has been around for a lot of time now and it has gained a very large number of users by now, and price it has is also to be mentioned, but beyond all that, we should always keep in mind that Bitcoin is not really backed by anything or anyone. If, lets assume, Bitcoin drops its value like hell and become worthless in a year or so, i know it doesn't sound realistic but if it can grow so rapidly it can drop like that as well, so if something like that happens, who will the people blame? Where will they go? What will they do? Since it all revolves around internet without any person or authority associated with it, we can only sit and cry over our losses if something like that happens.
Many people have been saying nonsense about bitcoin. I don’t know why they specifically target bitcoin, why not any altcoins? Those can also be thought of as a bubble. Not all the economists think it is a bubble but those who have passed such statements are either unable to understand the new technology or are puppets of government. Whatsoever the reason is, bitcoin is not a bubble and it is the future of our money.