Whether or not you should have a free plan really depends on your product.

In the case of trak.io, it's clear that the costs per user are too high for them to do it. Google Analytics can do it because it's backed by a big business and they can fund it. Many startups don't have this choice.

I'd just be wary of ditching a free plan. It's a great way to reach a lot of people with relatively little effort, just be careful you can support them with your business model.