Causal attribution is more valuable when you’re trying to understand the full journey rather than just the final click. I’ve seen how a retargeting ad might get credit with last-touch, but it was actually the blog post or early discovery ad that seeded trust. In SaaS especially, those first interactions often drive the conviction that later leads to demo signups. Bottom line: if you rely only on last-touch, you risk cutting spend on campaigns that quietly fuel conversions.