I don't know why people feel guilty. I've heard a few people say that they are fit enough to collect drugs, but that's really neither here nor there - the delivery services are businesses, and if it cost the NHS money to use them (more than it does to send items to a physical chemist) they wouldn't do it. Boots get paid to dispense medicines, and this is no different. Maybe they will start to charge in future, in which case people can opt to pick them up or continue with delivery, but as it is, the service is free, and I assume the cost of postage is absorbed into the pharmacy's profit margins.
I started using Pharmacy 2U during Covid, when the assistant in the Boots near my local surgery posted on FB every day moaning about having to be at work when others were on furlough, complaining about (sick) customers expecting their medication to be ready when they were told to expect it, and so on. There were huge queues to get essential medications, and no explanation as to why, when nobody was buying non-essentials such as hair products or cosmetics - if anything the pharmacy service should have been faster than usual. It's not as though they were dispensing Covid meds, as there weren't any. I had enough of it, and switched to delivery so my husband didn't have to wait in the cold to be served, only to be told that my inhalers weren't available. If they decide to charge, I will consider whether it's worth it, but for now it is definitely easier.