You still always see those panels in F1 that some guy is holding out close to the finish line.
Since they have constant radio communication around the track, I really wonder... what is their use?
Like here we see it tell Kubika he won the Canadian GP a few years back, but he probably already knows with the radio that he was P1?
There are many reasons for using pit boards despite radio communication.
The cars are not technically allowed to receive most information about the race via radio. Each driver knows their own delta from a dashboard display, but not the delta from the cars immediately ahead or behind. Boards are frequently used to tell a driver who is next in front or behind, and by how far.
Radios are distracting. Drivers complain already about the amount of chatter they get. This additional information is more time spent focusing on the sound and not on the road. Especially on tracks where there are few good long radio moments, which are also the tracks with many corners and passing chances, minimising the distraction is key to holding position.
... and pit boards can be ignored. If the driver doesn't care or is too busy dealing with an overtake or keeping a clean tight line, they can simply ignore the board entirely.
Radios break. Just like every other part of the car, the radio can fail and leave them helpless, unless an alternative method is available and is practised often enough to be effective.
