Good morning @m.trepka.
Sorry to be so late on the answer.
We can see this matter from an "awareness" point of view. This is the chart of the interest on the keywords "social trading" and "copy trading" searched on Google in the last 10 years.
It's clearly an uptrend.
Also, during this 10 years we have seen that almost any new forex/cfd broker was including social trading services in its offer. Plus, also old big brokers have implemented this type of services (FxPro to name one, with the SuperTrader).
This being said, I'd personally like to see some clear economic data showing how and how much the whole Social Trading sector has grown in these years. I haven't find any at the moment, in case I'll find some I will share it here
I personally don't know Motif Investing, but I know Peeptrade, and based on what you say, they look very similar.