Since about half the country seem to want to show up, it seems reasonable and proportionate. I wouldn't have a problem with some celebrity's funeral being a huge affair either, even if I didn't care for that celebrity myself.

In case I'm misunderstood, I don't feel strongly either way about the British royalty, but I'm OK with allowing a significant proportion of the population being left alone to get on with what ceremony they want to do, given that they want to do it.