Because TCP does far more things than UDP. UDP does not do flow control or congestion control or guarantee in-order and reliable packet delivery. TCP does all those things therefore it needs more functionality.
More Than Earthlings has 95 pages.
More Than Good Intentions has 320 pages.
More Than One Universe has 554 pages.
A Darkness More Than Night has 418 pages.
93 more
More than 400 pages.
Far more complex.
No a worm is more complex than a jellyfish
The Day Lasts More Than a Hundred Years has 368 pages.
Human cells are more complex than a paramecium. They are capable of doing more things than the single-celled paramecium.
Twilight has more pages than The Lightning Thief.
Temperate forests are usually more complex with more layers of vegetation than taiga.