personal email address

why do we need to get a personal email address?

Because many companies have email filters that block routine emails. Their own company may have such a filter and they do not know it.  They don't know it because emails to them have been blocked without their knowledge.

These filters are often "rented" from a software company.  

Example:

ABC financial company rents software to filter their emails form Proofpoint.  ABC financial company does not know which emails get blacked because they did not wrote the software--they rent it form Proofpoint. The financial professional working at ABC financial knows none of what is explained in this paragraph.