Probably because the general public got to learn a lot about Barry, either because of the TV show or the DC live action movies, around the same time that DC was doing the big flashpoint/new 52 change up that focused solely on Barry until Rebirth happened. Where as Wally’s big break to the public was around a decade or two ago when he was the Flash back in Justice League/Unlimited, unfortunately for Wally it was Barry who got the big public push around the time he was getting a big push in the comics.
That’s not knocking against Barry, I like Barry, I like all the main earth Flashes, but it just happened to be the perfect storm that occurred that threw Barry into the spotlight when he made his big return and Wally was getting taken out of the picture. Personally my hope with this new writer is one big flash family book, I hope to see Jay, Barry, Wally, and Bart all together, Wallace has teen titans so I think he will be fine with occasional appearances, and that all Flash fans can be happy.