Really, why can there be even 15 scouts in my team and NOBODY is flaring? On some maps we are blind as a mole without them and these games are won ALWAYS by team that has scouts actually using flares. They show enemy location for mortars, tank, aircraft and also give other infantry players a tip where they should preaim, so enemy will accuse your team for wallhacking because they can just look on the map and even start shooting before they leave the corner.
Flare has like 200 m range, so you can actually hillhump and not be useless if you flare for your team from time to time. Same thing with periscope. Also free points for assist + you can kill some people with them because they cause fire damage. WHY not to use them?