Significance as a social practicality
If only offers are binding, but not invitations to treat, then what is the point/purpose of a ITT?
An invitation to treat is simply useful pragmatically and socially. It allows a potential offeror to know that this is a setting in which offers (typically in relation to items noted in the invitation to treat, and on terms that might be included in the invitation to treat) are normal. The invitation to treat announces that the thing is probably open to being subject of a contractual transaction.
It would be perceived as odd to offer a shopkeeper to buy the shopping cart. Or to buy the entire roll or plastic bags in which people place their fruits or vegetables that they are buying. To make it clearer what is within the norms of the setting to buy, invitations to treat are common.
Why give it a name?
why is it a concept with a technical legal name no less?
Because invitations to treat have often been argued to be offers and it became useful to distinguish the two in common law reasoning. Finding a communication to be an offer has tremendous legal significance.
If something is an offer, the offeror is exposed to the risk of being bound to perform upon acceptance by the counterparty (or by anyone in the world, in the case of offers to the world: see e.g. Carlill v. Carbolic Smoke Ball Company  EWCA Civ 1).
If something is merely an invitation to treat, the person putting it forward has no risk in contract law of being bound to perform.
The distinction is nicely presented in AlumaSafway Inc. v The International Association of Heat & Frost Insulators and Asbestos Workers, Local 119, 2022 SKCA 99, at paras. 50-51 (citations omitted):
 An offer, in the contractual sense, is a “communication by the offeror to the offeree indicating a willingness to enter into an agreement with the offeree on certain terms”. Not all communications between two parties involved in a transaction are appropriately characterized as offers. Determining whether something is an offer requires attention to the existing context. The central question is whether there was an intention to create a binding legal relationship on certain specified terms, or merely an intention to start a discussion. In that respect, a distinction must be drawn between preliminary negotiations, or mere invitations to treat, and actual offers. It has been held, for example, that a mere expression of a willingness to contract on certain terms, or the creation of a draft agreement for discussion purposes, does not constitute an offer. As McCamus notes, “[t]he critical distinction between an invitation to treat and an actual offer is drawn on the basis that an offer communicates a willingness to be bound by the next communication of the offeree”.
 The test for determining whether a party intended to communicate an offer for acceptance is objective in nature. In that respect, the “question to ask is whether the offeree reasonably understood the communications, by words or conduct, of the offeror to constitute an offer. … The fact that the offeror may not have subjectively intended to enter an agreement is irrelevant”.
And then what consequences are there for maintaining a deceptive invitation to treat?
Where an invitation to treat also constitutes an advertisement or posted price in the context of consumer protection regimes, it can take on additional significance.
What constitutes an advertisement or posted price or other significant communication in consumer protection regimes is defined by statute and has only coincidental overlap, if any, with the concept of invitation to treat.
For example, in Canada, the Competition Act prohibits a seller from charging the higher price between two or more prices clearly expressed, at the time the product is supplied, on the product, its wrapper, its container, on an in-store or other point-of-purchase display, or advertisement.