Now don’t get this twisted, unknown app in this context mean any app that you don’t know its use, you only download it to see how it works without having any knowledge of it.
Sometimes you see certain apps and you are tempted to just download it. While it may not be a bad idea to download any app for testing, it is highly recommended that you know a bit about anything you want to download before downloading it. I know a lot of people are too lazy to read instructions and manuals (Me inclusive) sometimes it pays to know about something before jumping into it.
Now let me give you some reasons why you should stop downloading unnecessary or unknown apps to your device.

IT CONSUME YOUR DATA

When you want to embark on a journey of downloading unnecessary apps, be sure to get  enough data in your subscription because obviously you are going to be using huge data for no useful means.  I remember a ‘less techy’ friend of mine who subscribe for N1,000 data plan (350mb) and begin to download those crappy apps on Playstore homepage. Within 30 minutes, 1k is gone. Only for him to come to me and begin to shout that Glo have cheated him.  I ask him if he download something and he answered in the affirmative. But then I asked him what he is using the apps for and he said he doesn’t even know their use that he only wants to try them.
I know some people will still say that they can download anything because their data will soon expire and again let me emphasize that I am not against you downloading, but make sure you know what you are downloading.

IT CONSUMES YOUR PHONE MEMORY

Do you even need to be told this? I guess you don’t, but for the benefit of those who may not be aware, when you download anything into your phone, it occupies a certain amount of your phone’s memory, depending on the size of the file. Thus, you may end up with a slow phone or a device with insufficient memory. Your best bet is to uninstall all the junk apps and allow your phone to run smoothly.

YOU EXPOSE YOUR PHONE TO MALWARE

When you download any app that you have no idea of, you may end up installing an app that may damage your phone in the long run or even worst, steal your personal information such as passwords and credit card details.  So it is good to know what you are downloading in order not to expose your phone to any risk.

YOU WASTE A LOT OF TIME

Yes! The time you are using to download useless apps should be channeled into doing something that is more productive.  At least, you will use your time to do something more reasonable and at the same time, saving your data subscription.

YOU MAY BRICK YOUR PHONE

I remember sometimes back, I stubbornly installed Xposed installer even when I shouldn’t and I got my phone bricked. The version I was trying to install is only compatible with Samsung. Though I know, but I still tried it and afterward I seriously regretted it. What I am trying to say is that, be sure to know what an app can do on your phone before installing it. Else, you risked your phone being bricked.