Actually this is not a bad practice.
A lot of people (including Vim's doc as @B Layer's answer shows) argue that you shall not use arrow keys because it makes your hands move from the home row (the second line of your keyboard where you have hjkl) and that make you less efficient.
This is (IMO at least) a bad result from vim "purists" circlejerk: new users follow this blindly, some even disable the arrow keys and then they complain that they are not as efficient as before.
The only real rule to use vim is to use it efficiently: if you feel more comfortable using <left> and <right> than h and l be it, use the arrow keys. Vim even has set mouse=a option if you want to use a mouse!
Once you get used to vim and get better with the different available motions (f, t, ,, ;, w, b, e, ge, and basically everything in :h quickref) you might realize that you don't use arrow keys that much. And if you still use them, it's not a problem, use what you are most efficient with.
Note That the argument of don't leave the home row for more efficiency is not that good in my opinion: If you take a look at Why does vim use hjkl you'll see that these keys were choosen because there wasn't arrow keys when Vi was written. One could argue that maybe if the keyboards were different at this time no one would consider not using the arrow keys a good practice.