Royal the first born only gets more time while they are an only child. For many this is only the baby and early toddler years - often over before they turn 2 or 3.
As soon as the second is born the oldest seems massive and grown up, and many, many parents expect levels of patience, forbearance, understanding and unselfishness from a very young dc1 which they will never ask / unconsciously expect of younger siblings. Elders are always hearing "she/ he didn't mean to scribble on your picture/ break your favourite toy/ bite you/ spoil your sleepover/ interrupt you telling me something really important to you, say something upsetting etc etc - he or she is too young to understand, you need to make allowances/ be more understanding, you're the big one/ you're old enough to understand/ you should be worried about whether your little sibling is hurt, not upset that he's broken your treasured item etc.
The little siblings somehow always remain too young to understand, and the oldest always has to be the one with the emotional maturity to take what they fish out - woe betide an older sibling who hits back, no matter how small the age gap, the oldest is always wrong with some parents, regardless of how little the oldest is themselves. A 4 year old eldest is reviled for retaliating if a 2 year old hurts them but when that 2 year old is 4 they are still granted this special status versus the long suffering eldest.
UNLESS parents are actually aware they do it and constantly check themselves.
Youngest can end up missing out on 1:1 time definitely, but they are never expected to be grown up about a sibling hurting them, interrupting their heart to hearts, breaking their things, spoiling their games etc (unless perhaps the older one has special needs, in which case birth order roles can sometimes be reversed).