Starting with your last question first.
It used to be the case that if you needed to restore from an incremental backup then you had to restore from the initial main backup first and then do the same for every incremental backup. This would limit the number of increments that you kept as keeping a couple of hundred for example would involve a lengthy and time consuming restore. So it was up to you. With the latest version of Acronis you just restore from the latest increment and it just consolidates.
There are many reasons why Acronis is the backup of choice and too many here to list and it also depends on what other brand you compare it with.
I like it because I can do a disc backup and still access all the files within the backup but have to admit its getting a bit bloated and gradually losing its advantage over the free tools.
A popular free one is Macrium Reflect and there is also EaseUS Todo Backup.