Two households, both alike in dignity,
In fair Verona, where we lay our scene,
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
From forth the fatal loins of these two foes
A pair of star-cross'd lovers take their life;
Whole misadventured piteous overthrows
Do with their death bury their parents' strife.
The fearful passage of their death-mark'd love,
And the continuance of their parents' rage,
Which, but their children's end, nought could remove,
Is now the two hours' traffic of our stage;
The which if you with patient ears attend,
[Last line snipped]

you're right, of course; having gone to the trouble and expense of attending the play, an audience has an incentive to be more patient than a browsing book-buyer. Interestingly, the English novel actually grew up in the shadow of the theatre, and in the beginning modelled itself on the play. Older novels actually have fairly long introductions describing the setting, the props and the characters living their normal lives, before getting into the action.

Which is what makes this opening so arresting: it is simply loaded with hooks. It tells us there's going to be romance, conflict, bloodshed and tragedy, prefiguring the end but without giving away the plot, and introduces the MC's up front; and all in a sonnet!

It seems we are still learning from Shakespeare!

but I love reading shakespeare, because unlike when its performed, everything is to your taste and your specifications.