Double Standards

Why is it that it is illegal for automobile drivers to use cellphones while driving BUT there is no rule/law against bicyclists from using cellphones while riding their bikes?

For my American friends who read this blog and have never been to Singapore, just take any picture of China or India and that's what Singapore looks like these days. Actually, to the Bay Area residents, just imagine Critical Mass but with Chinese and Indians instead of hippie looking messenger boys and girls. Tons of bicyclists and many of them on cellphones, some of them losing their balance. It is just f**king irritating.