I understand that you usually could get away without reading the manual of a dive computer.
However, an issue I have seen happening to others is when **** happens and you go into deco or, on Suunto, you get deepstop by default.
When you are not used to it, and you have not read the manual, it seems that some people panic.
Someone in my dive group apparently went into deco accidentally then had to skip some of it because his buddy was OOA. He blocked his computer, but decided to do the second dive on his buddy’s computer.
When he told the story on the WhatsApp group, I couldn’t believe what I just read and explained to him the he was at risk of DCI and should definitely not have done the second dive. After talking to him it was obvious he didn’t know what the computer was saying.
I know that some of you will say that it was his fault for going into unplanned deco in the first place but discovering your computer in an unplanned situation ain’t great either.
Also I have met people who can’t tell if the computer is displaying a safety or mandatory stop. So although I think you can wing it and not read a manual, you definitely benefit from reading it.