Because they have other stuff they want to spend money on. Germany plans military spending hike, but is it enough to appease NATO?.
They are planning to increase spending to “above 1.5 percent” of GDP by 2024, not the 2 percent that NATO calls for (and that they agreed to). And they are talking about plans to improve readiness by “2032.” Putin’s Russia will need deterring before then.
Though German capacity building with NATO is more important than euros spent in the grander scheme of things, “it won’t help Germany any” in convincing fellow members, especially the US, of its commitment to the alliance, the European Council on Foreign Relations’ Gustav Gressel told DW.
And that the parties that make up the ruling coalition have very different ideas on the subject isn’t helping. For more on Germany and its commitment to NATO, see this link.