You're looking at it from the German perspective, but in reality the UK is in a different world on this.
The major concern is about overloading the healthcare system past its breaking point. The UK has 4,500 ICU beds, Germany has 24,500 beds. Based on a study in Wuhan, about 5% of cases require ICU beds, so Germany has the capacity to manage 490,000 typical cases (50x what they currently have) while the UK has the capacity to manage 90,000 typical cases (a little over double what they currently have). On top of that the UK has a shortage of PPE and testing capacity, leading to many more doctors ill or self-isolating and reducing the peak demand they can manage. The UK had no alternative because the infrastructure in place was dramatically inferior to Germany.
We already have
hospitals urging people not to go there because they have severe resource shortages. On lockdown. Surely everyone could see that would be happening on a much wider scale if not for the lockdown. It wouldn't simply have been a few old people losing a few months of their lives. It's the healthcare system that's at risk.
If we had 25,000 ICU beds then we would be able to cope without a lockdown, as per this graph on the top-left from
Imperial's modelling. Instead, because the ICU capacity is 5x lower, even with the most risky approach to suppression we will need to be in intermittent lockdown for 6 of the next 18 months, 1 month on, 2 months off.
Germany does have 25,000 ICU beds so they have more choice in that regard.