1. If outdoor ads in large towns and cities and transport advertising didn't work. Big brands wouldn't invest in them.
2. Of course brands understand their target demographic and only invest in advertising channels that work for them. So if you invest in London Underground ads for example, you will know what sort of 'opportunities to see' you will receive and the demographic that use the tube at various times of the day. Same if you invest in bus advertising or what we call ambient or outdoor ads in towns and cities.
3. And you are wrong, these advertising channels do get many repeat customers.
4. It doesn't appear that you understand how brand awareness works. Brands will invest in advertising in a number of channels that work for their target market - at football grounds, on outdoor ad spaces, promotions at train stations, in magazines, on buses for example as well on social media, editorial coverage etc. Collectively this will help build awareness of a brand and encourage brand loyalty and attract new customers. They certainly do provide a measurable ROI.