If that really is a genuine question, then here's the genuine answer.
People who have genuine selective mutism (and I am not saying this is the situation here, but just because you asked) have more issues with "basic politeness" words than almost any others. That is because different forms of communication have different levels of what is called "communication load" - that is, the "risk" attached to that speech, how much it relates to personal issues, and one's history/experience with that piece of speech. People with SM, and often autistic people too, are very sensitive to communication load, though they rarely would be able to explicitly say why some speech gets stuck but other times they are able to speak, but this is why.
For example, rote speech (eg reciting days if the week) or factual responding (eg what time is it, what is the weather forecast) are low risk. They are either known to be correct or shared from a direct trusted source. Reading aloud, assuming the person is a competent reader, again low risk.
Whereas giving an opinion, sharing a guess, these are higher risk (of being wrong, or displeasing the listener) and so more likely to trigger anxiety.
Professional speech is easier than personal speech, because it is less exposing of one's private self. For example telling someone the sales figures might be easier than telling someone what you plan to do after work. Because as a professional, one is one step away from the self. It's Katie the accountant giving those figures, whereas it's Katie the human revealing her after work plans, and that can be inhibiting.
Finally, words that have been a source of trauma are especially hard. These are generally 5 words - hello, goodbye, please, thankyou, and sorry. That's because these are the words a child with SM is placed under repeated enormous pressure to say, and given repeated negative feedback for not saying. "Say thankyou to granny for the present, or she will think you are rude". "Say hello to Jennie or she wont want to play with you". "You have to say goodbye to people, it's very rude if you don't". Hello has the added complication of being an opener and an invitation for further communication passes from the other person. Bye is marginally easier because at least it's an ending.
So no, it isn't always pretty simple to just say hi or good morning to work colleagues if you have SM. It's often one of the hardest things to do.