A lock for your bike can be awkward to carry and use. It also adds weight. But worst of all is completely forgetting to bring it with you! But concerns like this could soon be a thing of the past – if your bike IS the lock!
True, with an angle grinder or blow torch a thief could still take it (so ‘unstealable’ is little more than a catchy name for the concept). But wrecking a bike while stealing it is will put off a lot of serious thieves. Because considerable repair will be needed before reusing or selling on. Which is going to reduce the rate of theft worldwide.