It is better to do both of the things together with each other.Saving the money and also doing investements with some of those in the same time because with this you will make your money work and also will have some extra saved money.
I guess you are right with it, why you are just going to save only if you can invest too. But it is going to depend on the person on how he is going to be serious with his savings and as well as investments. Because there are some people that aren't able to manage both of it. They can only manage saving or investment only one of them.
Saving and investing are both important.
I for one make sure to save half my money. Meaning from what's left every month I deposit half to a savings accounts .The rest goes for pleasure or investing in bitcoins/altcoins.