Are you forced to buy windows in order to solve certain tasks on the internet e.g. like certain banktasks and to update garmin gps maps and other

[user1]

My conclusion is that in order to solve ALL tasks -and to use ALL 
websites on the internet you are FORCED to always have windows installed 
or to have an extra computer running windows.

Certain websites e.g. some online banking websites and other websites are 
not to be used by linux only users?

I would like to hear a proper statement about above from some of the 
really clever internet experts.

If above is correct, then all sites with linux installation instructions 
ALWAYS should inform, so new linux users will know?

THANKS?