A234 isn’t a very good starting hand in Omaha.
You’ll have at most one nut flush draw. If double-suited, you’ll have the low flush draw with very few blockers to high flushes to your non-ace suit. With no pocket pairs you can’t make a set. Any boats you make will likely be vulnerable to higher boats. If you’re playing the low part of a hi-lo hand, you may get quartered.
Good players bet with strong hands on every street, including preflop, regardless of game type. To illustrate this, the biggest pot in online poker ever was a heads-up pot-limit Omaha hand between Patrik Antonius and Isildur1. The blinds were $500-$1000. Isildur opened to $3K, Antonius 3-bet to $9K, Isildur 4-bet to $27K, and Antonius 5-bet to $81K. When Isildur called, there were 162BB in the middle before the flop. That’s simply not possible if players aren’t betting preflop in Omaha - and I think we can all agree that Isildur and Antonius are among the best PLO players in the world, or at least they were at the time.
Yes, sometimes you’ll raise preflop and the flop will miss you. However, when you’re ahead of your competitors’ ranges, choosing to limp instead of raise allows your competitors to catch free/cheap cards, and creates less of an incentive for them to fold off their equity. That’s why good players always raise their good hands preflop in Omaha, while weak players never do.