1, bitcoin has no value, just a piece of junk number. it has no value like currency or gold, people buy it just for speculation.
all value is subjective, the fact that people are willing to trade goods for bitcoin show that you are wrong and it does have value.
your statement about people buying it only to speculate is backed by zero evidence.
2, bitcoin is unsafe and easily be stolen. If someone buy some coins for invest, it may disappear or hacked.
bitcoin is the safest asset in the world, for 120$ you can buy
http://www.bitcointrezor.com/ and get the same security as the computer that is responsible for launching nuclear missiles.
it doesn't get anymore secure than this.
3,Gov will ban it, because it is anonymous and can not be controlled. People can use btc buy illegal goods like drugs and guns, and may not pay tax. Or terrorists will use btc to fund terrorism activities.
you are wrong, governments are not banning it, and even if they did there is no way to enforce such a ban.
4, Btc system is unsafe too, 51% attack will destroy it.
a 51% attack can't destroy bitcoin even if it happened.
it has never actually happened and can only happen in theory, there is a much higher chance that your government will freeze your bank account and steal your money like they did in Cyprus.
5, people does not need bitcoin, they can use dollars as well.
the dollar is already dead.
http://www.usdebtclock.org/the only way out is inflating the dollar to zero.
So I think btc will soon die.
go ahead, keep your paper money, remember we warned you when it becomes worthless.