Some aircraft have VS as the only sensible pitch mode in the climb. You learn fairly rapidly to actually fly the aircraft. Another example of automation makes you lazy.
A major harp-tailed loco recently issued a memo to the effect that use of VS in the climb was streng verboten except when rocketing towards a cleared level as I imagine they have had the odd low speed event related to it.
Such events are indicative of very poor mode understanding, monitoring and common sense, despite the sensible mode reversion logic built into the 737 which should protect you.
In flying bizjets solely in VS and without autothrust up to 490 we never had any speed events (in an OFDM monitored operation) whereas it seems to happen with depressing regularity in more automated airliners, albeit with a far larger fleet and higher sector numbers.