They’re actually not tea at all, they’re tisanes, a pleasant French word that means’herbal infusion.’ They should be called such and labelled appropriately in stores.
Tea is, properly a plant originally from China: Camellia sinensis. How the word came to be used as a descriptor for any hot drink in which leaves were infused or decocted, I don’t know, but it’s lazy language; misleading and dishonest.*
Tea drink is, of course, an infusion, but not all infusions are tea. If it doesn’t contain actual tea leaves, it should not be called a tea. Period.
The original word tea itself (te and its Cantonese equivalent, cha) have specifically meant Camelia sinensis in China since at least the eighth century CE. That’s what they meant when European traders started bringing the stuff back. The Online Etymological Dictionary explains some of its European use from the 16th century:
The distribution of the different forms of the word in Europe reflects the spread of use of the beverage. The modern English form, along with French thé, Spanish te, German Tee, etc., derive via Dutch thee from the Amoy form, reflecting the role of the Dutch as the chief importers of the leaves (through the Dutch East India Company, from 1610). Meanwhile, Russian chai, Persian cha, Greek tsai, Arabic shay, and Turkish çay all came overland from the Mandarin form.
First known in Paris 1635, the practice of drinking tea was first introduced to England 1644. Meaning “afternoon meal at which tea is served” is from 1738. Slang meaning “marijuana” (which sometimes was brewed in hot water) is attested from 1935, felt as obsolete by late 1960s. Tea ball is from 1895.
“Herbal tea” might be derived from the Latin: herba thea means “tea herb”(LAtin was still more-or-less a living language in the 16th century) or maybe it, too, came via the Dutch traders: herba thee (which also means tea herb). Either way, we ended up with “herbal tea.”
Whatever its origin, it is incorrect. It’s like pointing to a dandelion and calling it a rose garden because they’re both plants. Or handing someone a cola and calling it a cold coffee because they both have caffeine. The only thing tea and tisanes have in common is the hot water.
Why aren’t these non-tea infusions called “herbal coffees” of “herbal colas”? That would make as much sense as calling them herbal teas.