Many companies still use mass mail outs as a way of getting in touch with their customer base or potential customer base.
Before the days of the internet, the majority of marketing was done by letters mailed out, leaflet drops, phone calls or door to door sales. Paper mail outs could end up being very costly and many businesses struggle to see a health return on investment. One of the biggest issues with print work is making sure that it is all correct before it is printed as unfortunately unlike online publications, you normally will have to pay for the whole job to be corrected and printed again or send something out that contains mistakes (which does not give a great first impression of your business).
Door to door sales people can also be expensive and if you do not have the right people for the job or do not go to the right houses then you may find you have very little uptake. You may have two or three field agents out a few days a week and only generate one sale containing a small profit. Once you have taken in to account the salary that you are paying the members of staff, you will probably have not made any profit on the deal.
Despite this, there are still a number of companies that find that mail out work well for them, especially if they have a good solid database to email to.