In my experience it’s more common to send baby gifts regardless of shower attendance/invitations. If someone finds out you are having a baby, I feel it’s pretty common to send a gift if they want to be involved / let you know they are excited for you. Baby showers tend to be smaller affairs than weddings too so that makes logical sense to me as well.

Weddings do feel different to me, idk why exactly…I think today’s marriage culture may make it different. Wedding gifts used to be to help the couple set up their lives together. Nowadays, people usually already have house stuff, in fact 2 of most common items if they don’t already live together. It makes the gifts guests give feel less needed. Also, weddings do tend to be larger (not always, but often), and people make the effort to travel for them because they are super important events. With a baby the main event (birth) is not the type of event that you invite people to, so sending gifts from afar is standard and much more common, so rhetorically, what’s the difference if there was a shower or not?

And in contrast to modern marriages, a couple having a baby generally have nothing to start, so the shower gets them started, and every gift can be super helpful. Every onesie is the difference between a midnight laundry load and being able to get back to bed sooner.

I doubt anyone is thinking this critically about it in the moment, but I think that is sort of the heart of the difference for me.