Running a large discount or lifetime deal allows you to drive significant amounts of users (and revenue), which can later be upsold for revenue expansion or leveraged for network effects.
Referral programs take your best customers and turn them into salespeople.
Becoming part of an ecosystem is a great way to find distribution and out-compete your competition by being easier to find and implement.
Many training programs and communities offer membership perks, which include discounts and trials of tools and services. Become one and get users and sales.