In the 2020 update of the Scrum Guide, the Sprint Planning section has had a very welcome update. Every part of Scrum has a purpose, a reason to why it's included in the framework, and this update made the purpose - raison d'etre - of the Sprint Planning clearer. Let's see how!
Every Sprint is an investment. We invest money and time to market, and we typically can't take it back. What's spent is spent. Scrum requires that we have an idea of the value of these investments. We craft a Sprint Goal to answer this question:
- Why do we invest in this product/service? What outcome or impact are we looking to make, with this investment?
We find the answer to this Why-question, in the Sprint Goal.
OK, given that we understand the objective - the reason for running this Sprint - let's come up with our current best idea of what to do, to get there. This commonly means we select backlog items that we best think will realize the value we're after, helps us achieve the Sprint Goal. So we come up with a forecast of what we want to do, in order to achieve the outcome we're investing in.
Nice! So given this forecast, how are we going to get the work done? Where do we need to research, collaborate, design, re-use, throw out, ... or simply "just get X done", ... The 2017 update included the language "enough for next 2-3 days of work", which was a clear hint of the waste you likely get, as you try to plan complex work in great detail. When there's lots of unknowns, planning to a high level of detail usually means we have a high amount of waste.
The 2020 update is less prescriptive. You'll need to make an interpretation of what "plan the work necessary" means to you, and inspect & adapt your way forward ... which is the core of Scrum, right? Inspect & adapt!