While it's very hard to measure the effect of ads trying to create this loyalty, it doesn't mean that it's not worth it.
I've discovered that for myself where I saw ads on Facebook that I didn't click, but later saw a product in store and tried it out. If you just follow conversions, you'd say that the Facebook ad was worthless, whereas it actually influenced my buying decision.
I'd argue that most money on ads is well spent, but to be effective, you must have a huge budget. People need to see your ad multiple times, so that they'll be familiar with a product. If you don't have that budget, it'll be very hard to use ads effectively. But that's no fault of FB or Google, that's just psychology.