FWIW part of the reason you're seeing that is, at least traditionally, APM companies rebranding as Observability companies stuffed trace data into metrics data stores, which becomes prohibitively expensive to query with custom tags/attributes/fields. Newer tools/companies have a different approach that makes cost far more predictable and generally lower.

Luckily, some of the larger incumbents are also moving away from this model, especially as OpenTelemetry is making tracing more widespread as a baseline of sorts for data. And you can definitely bet they're hearing about it from their customers right now, and they want to keep their customers.

Cost is still a concern but it's getting addressed as well. Right now every vendor has different approaches (e.g., the one I work for has a robust sampling proxy you can use), but that too is going the way of standardization. OTel is defining how to propagate sampling metadata in signals so that downstream tools can use the metadata about population representativeness to show accurate counts for things and so on.