Well for starters, the value of silver and gold is way too high to actually be used as an everyday currency. A single full gold coin could be worth thousands of dollars and who's going to be carrying that around in their wallet or purse.
There's also the fact that the value of gold and silver us usually a function of their purity and purifying these things aren't very cheap. You also have to take into consideration that moulding these things into small sizes which can easily be exchanged is also quite expensive.
Moreover they'd have to be made into extremely small sizes before they could be worth small values that can easily be exchanged between people. Using them as currency simply isn't feasible anymore.
I think mainly because of its value. Both silver and gold have high values, especially gold.
In here, per gram of gold in jewelries is about 2,400+ pesos while silver is about 25+ pesos. Therefore, using it on coins will not be possible especially for low denomination coins.
The value of these precious metals also varies or changes and using it for coins could also affect the value of coins as well. Which is not a good thing for common circulated coins.
That could be why nowadays, few gold and silver coins were made mainly to commemorate events or people, and just for collections.
I think the main reason is because everything is digital now... Just think about going to a bank... And all that stuff... I think of it like the begining of Fiat currency... Then it's not practical at all.