Here in the uk they just took the old £1 notes out of circulation and replaced with a £1 coin. so you had no choice. Just recently they replaced the coin with a new design and the old one you can no longer use as tender in shops. here canada is now gonna be removing notes from circulation after passing some bill. all fiat though these days unlike coins of the past and no silver in ours now.
Why do you think they are replacing the notes with coins ? Because a $1 notes "lives" only for about 18 months while a coin "lives" for 20 years. So, for the government, the cost of coins is far lesser than the cost of notes.
Now we got polymer notes £5 and £10 so £20 be next out as they last longer as well. won't be long till it's all just electronic deffo by 2050
In Canada all the notes are plastic and the coins go from 5c to $2. I will give you a hint why in USA they still use the $1 bill : who is the supplier of the banknotes to the Bureau of Engraving and Printing ?