Most company newsletters operate with a 25-30% open rate. Is it honestly worth the effort to send it out when only a small minority of  users will open and read it? 

I say “yes” because of the nature of the 70 to 75% of readers who do not open the newsletter.  This may be a group of people who did not open the last newsletter, but they are more than just that. They are also a group that opted onto your mailing list, not opted off of your list, now remain on your mailing list, but did not open the last e-mail you sent them.

Why would customers do all these things? When a customer does not open a newsletter it might mean they are busy or traveling. But more often, it means they are not focused on the kinds of products and solutions you offer. Customers are not focused on buying products from you all the time. 
If you make construction materials your customers may be involved with a lot of other responsibilities. They may not open your newsletter because they are involved in maintenance issues but will return to when their job demands it.

What if your company could buy a list of customers who were interested enough in your product category to subscribe to a newsletter, were not were not actively involved in  buying products right now, but would return to buying eventually. Those customers would comprise  a pretty good mailing list.

Instead of calling them deadbeats who don't open your newsletter, think of them as latent customers who will return to your area of interest, open your newsletter, and buy from you all in good time.