This shows an evident increase in the adoption of Bitcoin all over the world, although unique addresses does not necessarily translate to unique users of the network, it shows the growth of the network.
It is evident that with more time there will be more users in the market and people will be storing their coins in different addresses and as you said these unique addresses does not necessarily mean that these are unique individuals holding the coins and many people hold their coins in different address for privacy reasons and the main thing you have to identify is the number of transactions per day and we are not seeing much different in that.