So why learn sums when we have a calculator or phone? Why learn to spell when we have spell check? Why learn to draw with traditional tools when we can draw digitally?
This is certainly a perspective I'm familiar with and honestly I cannot fully give an answer that satisfies those who pose it. I see these concepts as a reliance which have knock-on and cumulative effects. I know that as a child, if my Mammy had always given me the answer to a questions immediately and hadn't encouraged me think on it to find one in my own way, there would have been aspects of my own capabilities I wouldn't have discovered. In a way I could liken the concept to a person who visits a foreign country to take photographs rather than just doing an online image search.
But that's a false dichotomy. You're not using any fewer skills by finding information online. Reading something in a book and reading something on the internet are virtually the same skill set. The source is the only difference, along with access to that source.