First of all for some reasons appears odd because there is a very similar phrase - for some reason (reason without 's') - meaning that there may be a reason but the reason is presently unknown. Clearly this is not what the writer intended in the opening example!
Secondly, there is a slightly different phrase that is often used in this situation - for several reasons - meaning that there are several possible reasons. Surely this is what the writer meant to communicate? The reasons are known and the writer is going to share them with us.
The workforce at DJ Computers has become smaller in recent years, for several reasons. First of all, the company has been forced to make staff redundant following financial recession. Certain staff will not lose their jobs because their work is essential to the company. Various other staff, however, are less essential, and management will consider a number of different criteria when deciding who will stay and who will go.
Use these alternatives flexibly in your IELTS writing and you will improve your score for LR (Lexical Resource) and possibly also for TA/TR (Task Achievement/Task Response). If you're not sure what is meant by LR, TA and TR, take a look at the IELTS public band descriptors for Speaking and Writing.
By the way you might also notice that staff is used here as an uncountable noun, which it is - most of the time. I talk about staff in more detail in a separate post.