Integrations with ticketing/CRM systems. You can hit the high notes, and go for the handful of most common ones, but it's always a temptation to chase a deal and promise another one. Pretty soon, you're spending all your time chasing down things in a half-dozen or more systems, that all have their own idiosyncratic SDKs or APIs, which change at unpredictable rates. Moreover, to do development and testing against those systems, you've got to keep those environments up, and seeded with test data. Some of them are cloud-based, and you can get a free/low cost development instance, but others are big, unwieldy on-premise deployments that require a host of servers to run all their gunk - with costs in server racks, provisioning time, setup time, and non-core expertise in keeping that crap going.