Industry segmentation then targeting sales resources to segments. Those resources are your salespeople, ad materials, trade-shows, etc. The industry segmentation is prioritized for segments that benefit the most from the product and have money to spend. You don't focus on the markets or company sizes you want. You focus on who really needs your product because it really makes a difference in their bottom line.
There have never been more brick and mortar, grey haired experts available for hire to SAAS providers. These folks have the domain expertise to look at your product and provide the message, network and outreach to grow your user base.
I cringe mightily reading SAAS job postings looking for someone with business development (or marketing) experience but without industry expertise. Is it agism? Not sure, but I had this experience interviewing for a Marketing Director role with a major Valley SAAS firm who opted for a generalist and who I understand hasn't seen more than 10% growth since. Sometimes the hard way is the right way.
This was a bit ranty, but it's been on my mind for some time.