VirtualBox has it's own advantages, for starters some people may find it's GUI easier to use. It also has certain unique features not found in other opensource hypervisors, such as seamless mode. Finally, VirtualBox may have better compatibility or performance with certain operating systems. For instance, in my case when I wanted to get GhostBSD working on virt-manager, I ran into lot of issues, such as not being able to install it in UEFI mode, mouse not working etc, whereas it ran and installed without any issues at all using VirtualBox.
I have heard of Oracle looking at IP addresses and if they notice a trend they try to collect a license off it. Same crap they do with Java. Do people use VBox and not concerned of Oracle looking over them?
Yes that is indeed a thing Oracle is notorious for, but with VirtualBox the only concern is with their proprietary extension pack. VirtualBox itself is licensed under GPLv2, so there's no issues using it in a commercial environment. However, the extension pack is for personal use only. Luckily, the extension pack isn't really a necessity any more - back in the day, it was needed for USB 3.0 support, but now it's only needed for VirtualBox's built-in RDP, disk encryption, Intel PXE boot ROM, and webcam passthru. If you don't need these features - which most people don't - then you can use the main VirtualBox package without any worries.