How are futures/options standardized with amount but stocks arent?

I heard that exchange-traded derivatives like Futures and Options are traded with a set number in each contract, meaning every options or future contract, you can buy a quantity of 100, no more and no less.





How come stocks and bonds are not the same way? How come there is no pre-set limit to how many you can buy once entering a contract?





PLEASE HELP!!!|||Yes, you have to buy in sets of 100. I don't know why.





Stocks are shares of ownership of the company. Value could change.





Bonds are IOUs issued by the company to investors. Each bond agreements sets a fixed interest rate with no chance of change. But since bond rates for new bonds have different interest rates, you can sell your bond to someone else if your interest rate.