Do you really think they don't???
Think again...

They clearly have an intention to convert fiat black money into Bitcoins directly in order to let it look clear and safe...
This way, many people will have anonymous accounts due to which even Governments won't be able to track those Black money Bastards without the consent of this bank...

Banks are not suitable, agreed, because Bitcoin is made to have our own bank in our hands itself...
But what do you mean by transparency, or you are trying to say make it centralized and show records for the same in Banking regards???

but surely they won't only keep bags of bitcoin, they are gonna become a big whale this way and they will be able to ride the market as they want and earn huge profits this way

Not everyone hate banks <<Did I just say that?>> Most Bitcoiners still use banks for things like mortages and loans and the payments requiring the fiat system.
If they combine the two, they might grab a share of the market, currently held by banks that does not allow Bitcoin.
If I am forced to use a bank, I will rather use a bank that are pro Bitcoin. How many people had already had their bank accounts frozen, when it was linked to Bitcoin? They spot a gap in the market, and they capitalized on it.
Take the business away from the banks, who does not acknowledge or allow Bitcoin users.    

According to some of the private authorities Swiss banks have 8000000000000$ of black money from our country.
If they will convert this money in BTC i think value of bitcoin will definitely rise.

A Bitcoin bank could provide currency conversion services so you can have a debit card, direct deposit, write checks, etc.

You write a check for dollars, it gets cashed and bitcoins in your account are converted to whatever currency the check was made for. Same for debit cards, etc.

Whether we like it or not, huge numbers of people could never be bothered to be their own bank. They're more worried about their anal fissures or Taylor Swift's next outfit.

Bank-like entities are an inevitability. Most people don't want to have to think about securing that shit.

Bitcoin is internet of money. It helps you to transfer some value far with low costs. Bitcoin is not a Bank. Lots of people that dont know what bank really is, thinks that bank is what Bitcoin can do.

If anyone thinks that there will be no banks with bitcoin is really wrong. Banks will use internet of money fro their services. What is allready in Bicoin will just not be their services anymore.

A lot of people don't want to hold their own BTC because they don't trust themselves, and they want to have someone they can blame to if they lose their Bitcoins, since they don't want to blame themselves in the case they lose them. That is the reason Bitcoin Banks will be somewhat successful.

if you think about it any exchange can be considered kind like a bank, if you hold money there, many are just less secure than others

banks are welcome only if they can offer a 100% secure investments with bitcoin..i'm talking about interest like with fiat

but this will surely bring, the already little portion of the bitcoin anonimity, down