A few reasons.
One is that the modern left is strongly allied with corporations, the mainstream media, and corporate censorship. BLM, for instance.
Another is that these leftists base much of their rhetoric about social issues on a vulgarised form of capitalism's rhetoric. For instance, capitalism often brought an emphasis on the language of 'rights,' and the concept of negative freedom. Socialists typically take this concept and corrupt it into pure arbitrariness, hedonism and caprice, as for instance with transsexuals and their 'right' to their gender identity.
This leftist version of 'rights' is not concerned about social order, and will allow atomised individuals to trample all over society and reality itself, for instance by redefining 'gender' and thus nature based on however they feel or by regulating social conduct based on the feeling of 'offence' whether or not it has any basis. In this sense, it's not surprising that they would occasionally fall back on the basis of their conceptions, capitalistic private property, when they can use it as a vehicle for their own arbitrariness. They want to let gays do whatever, let trannies do or be whatever, and if the 'rights of private companies' can give them a pseudo-official stamp of approval then they figure that it's one step closer to importing their fifty hundred genders into reality itself. If private companies can do things for no reason, then maybe they can add a few hundred genders? Past a certain point, modern leftist ideology needs a way to express itself arbitrarily because it becomes a pointless, irrational hodgehodge of identity politics, gender identity preference, and cancel culture.
However, this focus on the 'rights of companies' tends to disappear often, such as when blacks are rioting and burning down businesses. Since it isn't a vehicle for leftists' own agenda here, they mostly dispense with the concept.
They can hence tend towards rhetoric resembling that of libertarians, and might well resemble several libertarians, but in general the leftists have much less commitment to these ideals. Libertarians might support others' rights to express things that they abhor, but modern leftists often just want to 'bash the fash' and hate on Orange Man.