My son is 7 years and he routinely asks me "why learn anything when you can just ask Google?". I can only imagine the impact this will have on that attitude over time.
1. Knowing things lets you know more things faster and they stick: associative memories are very durable because they are mostly groups of references to existing objects in memory. Much less novel information that needs to be encoded. Repetition and memorization matters.
2. Look up latency: Same problem as computer cache misses and L1 vs RAM lookup times. You will take 100x longer to achieve the same result by looking up reference material all the time. Also important questions typically have answers from many different problem domains (social, scientific, philosophical, ethical) and its important to have a lot of knowledge memorized to see a solution to a novel problem holistically.
I try to impress upon him too that some things take hundreds of hours of explanation before you know enough for it to be functionally useful to you, so you can't always just Google everything. You have to learn things and build your foundations up. Alas he hates the idea of learning anything.