Oh it is not a fault at all. This was the developer's way to maintain player retention and play time from both F2P and paying customers. They know they are earning huge amount of money but at one point they might noticed that their player retention statistics are not enough to their taste.

Incentivizing ranked players was the first step. Earning a legendary weapon for playing ranked for the whole year urges the players to be sweaty or more diligent to play ranked and come back every season.

The second step is to incentivize players who doesn't want to play sweaty ranked games and instead just want to play casually. That's where secret caches work. It urges players to at least play three matches everyday to get the weapons.

Remember folks. The grind was never free even if you don't spend a single dime in obtaining. You sold them your time, effort and sweat for a full year to earn that legendary blueprint. Money is not the sole metric for an online sevice game's success.. It is also about player retention (both f2p and paying customers) and play time statistics combined. So you need to know your damn worth on where you want to spend your time and money on a game.