Yes, travel insurance is worth having for a trip to Antalya, and the honest reason leans toward cost and disruption rather than any unusual danger along Turkey's Riviera coast. Antalya draws visitors to sights like the Duden Waterfalls just outside the city and the old town of Kaleici along the harbor. A policy here mainly smooths over the gaps a resort trip can expose rather than guarding against serious danger.
Turkey is not part of the European Union, so EU and UK reciprocal health schemes like the EHIC or GHIC do not apply here the way they might elsewhere in Europe, which makes a standalone policy the only real safety net regardless of where you are traveling from. Turkey also has a large private hospital sector geared partly toward international patients, and facilities in Antalya are generally well equipped for routine and moderately serious cases. Private care abroad is rarely free even when the quality is high, and some facilities expect payment before treatment; check that your policy pays hospitals directly or reimburses promptly rather than assuming a public-style system will simply bill you later.
Summer heat, roughly June through August, is intense enough to be a genuine health consideration for older travelers, young children, or anyone unused to Mediterranean sun, and the wider Turkish Riviera, including areas near Antalya, has seen serious wildfire activity in past summers that disrupted travel along the coast. Confirm your policy covers heat-related medical treatment and any weather or wildfire-related trip delay before a peak-summer visit.
Check whether your existing health cover extends abroad and specifically to Turkey before you travel, since coverage rules vary by country of residence and this page cannot confirm your own plan's terms. Keep any clinic invoices, treatment reports, and receipts for medication, since Turkish providers generally issue standard paperwork on request, and many policies want notice before non-emergency treatment is booked rather than assuming automatic reimbursement afterward.