They're a much undervalued marketing communication; keeping you in contact and front of mind with valuable clients, prospects and suppliers.

Grow your sales
Generate business leads & enquiries
Drive traffic to your website
Raise your business profile & that of your brand(s)
Build relationships, recognition and trust
Position your business as the expert
Inform / up-sell your latest products & services
Provides a reason to keep in contact - even through a long sales cycle
Build relationships with clients you wouldn't otherwise talk to... particularly useful if you have a large database