At least partly because Joppa was not a Hebrew city. From Joshua 19:

The seventh lot came out for the tribe of Dan according to its families. 41 The territory of its inheritance included Zorah, Eshtaol, Ir-shemesh, 42 Shaalabbin, Aijalon, Ithlah, 43 Elon, Timnah, Ekron, 44 Eltekeh, Gibbethon, Baalath, 45 Jehud, Bene-berak, Gath-rimmon, 46 Me-jarkon, and Rakkon at the border opposite Joppa.

Instead, it was a Philistine city, at least eventually governed by Ashkelon as seen in the Prism Inscription of the Assyrian king Sennacherib:

Sharru-lar-dari, son of Rukibti, their former king, I set over the people of Ashkelon and I imposed upon him the paymenr of tribute (in the form of) presents to my majesty. He accepted my yoke. In the course of my campaign Beth-Dagon, Joppa, Banaibarka, thr cities of Sidka, who had not speedily bowed in submission at my feet I besieged. I conquered. I carried off their spoil.