Why do all your systems transmit only 10mW?

Because in Europe, like in most countries in the world, the maximum radiated power allowed for analog video transmitters in the 2.4GHz band is 10mW. Unlike in the US, it's not possible to get past this limit by getting an amateur radio license. And as it's illegal to sell radio equipment that doesn't comply to the CE rules, we can not sell more powerful transmitters.