The downside is that you lose agency as you are wholly reliant on someone else to wake you up.
The type of ships that run a Cr700 low berth might be the ships that decide to take 100% profit and just space you or sell you to slavers.
Even on a legit ship you are especially vulnerable if the ship suffers a malfunction. Awake passengers can get into a lifeboat, low berth passengers could not be revived in time, even if the ship had enough space in any lifeboats or pods for them (think Titanic, you are cargo class). In the event of pirate attack you are neither useful in defending the ship against boarders nor able to influence what the pirates do to you if they win. In the event of a power issue, you could all have an unplanned revival or just die there.
These are not regular experiences to make it a per trip dice roll, but they would only need to happen for a fraction of passengers to put some people off. How many people avoid flying where possible despite the proportionally low incidence of air accidents. I avoid ocean travel as I am terrified of depths (who knows what is lurking down there - I blame Lovecraft!)
Regular passengers can have their life support adjusted incrementally during travel to match their destination world. In low you could go from high oxygen, low gravity tropics to, low oxygen, high gravity semi-frozen within the blink of an eye as far as you are concerned. Even if the assumption is that the low berth alters what it is feeding you, the psychologic shift cannot be managed incrementally.
Actually just bunkering up for a week can be very relaxing - more so than a vacation. Not everyone likes it, but for some that week in a cabin with only your own company, good food, a good book and maybe a project that you have been putting off could be blissful.
Just because you don't die it doesn't mean it is a pleasant experience either. Most people survive general anaesthetic but I wouldn't choose it to avoid the boredom on a long haul flight. Falling asleep during air travel is disconcerting enough for me when I wake. It is not a vacation it is sleeping for a week. Regular travellers will doubtless suffer side effects like muscle atrophy, possible mental health issues.
To sleep—perchance to dream. Aye there's the rub. For in that sleep of low berth what dreams may come