Supporting developers or community members of an OSS project your company uses through employee time or financial means is less of an investment, and more of a hedge. You've picked up a product off the shelf, however that product has a future direction decided by a number of people in a community.
A company that chooses not (through inaction or action) to participate in the project is relying on the existing powers-that be, and their existing influences, to make decisions that will benefit the company. This is a risk.
A company that chooses to participate cannot control a decentralized project, but they can absolutely influence the software and community by choosing what projects to fund, what kind of roles to hire for, what projects to sponsor, and what to publicly talk about. This influence nudges the community in directions beneficial to the company, and ensures the project doesn't head in a different direction.
For example in the last year the Ember.js community has seen an influx of larger companies hiring positions that include OSS time for employees. Large companies sponsoring OSS work is becoming more common. This means the parts of Ember that benefit large company needs (lots of devices, big dev teams) are getting more focus. The transition is exciting and fascinating to observe.
Support OSS projects important to your company, or accept the risk that comes with allowing foundational parts of your business to be managed by others (without your needs in mind).