While I like Lucretius diplomatic answer, there's also a Randian one that is more likely to arouse hostility itself - an answer that should be obvious to anyone standing on Objectivist theory.
I take "Rand is ignored by academics" to mean "Rand is ignored as a philosopher by established philosophers." - as opposed to IT professionals, for example.
I use the term "established" to talk about philosophers who either have a tenure at a university or is accepted by those who do. That excludes people like Stefan Molyneux on YouTube and his own "Freedomain Radio", who calls himself a philosopher and even makes a living on it by accepting donations, but is probably as least as disregarded by those I call the established ones as Rand was and still is.
Now put yourself in the shoes of someone who works for a university: You are knowledgeable in your field, but your skills are difficult to market. Your income depends on your status as an accepted member of academia and that traps you: In contrast to shop owners or professionals, you can't just relocate somewhere else, another country even, unless you'll find an educational institution there that accepts you.
The funding of those institutions (at least as far as philosophy is concerned) depends on either the government or voluntary donations - as philosophy and many of the social sciences have little to no funding by the economy.
If you are in such a situation, would you rather like ideas ranging from social contract theory to communism, ideas that support the notion of unconditional funding for those institutions (and by extension yourself) and so give the necessary taxation the appearance of moral justification, or would you rather be attracted to Ayn Rand, who openly condemns such things?
This explanation doesn't only explain the hostility towards and rejection of Ayn Rand - in fact it explains quite a lot of why certain ideas achieve popularity in established academia and certain others do not.
Austrian economics, for example, have a hard time gaining popularity among US academics. In the German-speaking world they are even less popular - ironically.
Communism and racism are the most obvious examples of something that once was popular in academia and both are sets of ideas that maintain that certain groups of people should "stick together".
Austrian economics, to make an example to the opposite, imply that state interventions cause more harm than good, ie that collective action is bad: Would you like to hear that as someone whose income depends on exactly that? Keynes may support capitalism, but at least he claims that there has to be someone to spread money around in times of depression and obviously those people need a steady pay cheque.
It's important to realize that these thoughts are not conscious plans. People like certain ideas and dislike others. It is immaterial that many who like collective action and support collectivist tenets in the end don't benefit from them. The theory still explains why they liked them in the first place.
For example, an established philosopher might passionately argue for a stimulus in times of high unemployment or for a draft in times of war even when he's not going to benefit from the stimulus in any way or might even have a son harmed by the draft. He argues that way based on principles he holds - but principles he might have been attracted to because of his situation.
And for anyone who himself stands on Objectivist tenets, it should be obvious how only a few strongly influenced that way can drag a whole society into a specific direction: Most ideas held by an individual are not verified or even originated in his mind, but adopted second-handed:
Many people who one wouldn't suspect to be attracted to certain ideals are living and working in a social milieu where those attitudes are generally accepted. Those will need a strong motivation to deviate from them in their own world-view. For example, you will need a strong motivation to begin to believe that taxation is a form of theft when everyone around you considers this notion to be absurd.
From a bird's eye view, this phenomenon of intellectual cohesion among people is the Zeitgeist. Rand was pulling that Zeitgeist in the opposite direction of those she was ignored and scorned by - which isn't surprising.