There Is a big market out there, those in their 50s-60s who only want to use a smartphone for
Phone call, SMS, whatsapp, check 4d-toto, take simple pictures, play the jackpot or sudoku, big screen to read a bit of online news, watch tv serials on it.
Do they need nfc? Do they use it for Internet banking? Do they do high risk transactions?
They just need a decent phone at an effective cost. Which xiaomi is targeting this segment of market, the everyday average users who don't need much.
Less than $300 and is able to perform 80% of the tasks adequately with no risk to security or any implications.
Security risk or bugs are probably things that even bothering theses folks because even if it exists to them, they are not using those functions which affects them much. Therefore xiaomi is also slow to do updates too.
So to those people who thinks that security patches and bugs fix are important because they are dealing with a lot of sensitive stuff or lack of such fixes is going to affect them much, then i think xiaomi is probably not the best segment to go for.