OK, let's try again...one more time.
A series/parallel setup of house batteries on a (larger) cruising sailboat may be advantageous because:
1. lower "depth of discharge" in real world usage (far from a fallacious argument);
2. lower acquisition cost;
3. smaller size...will fit where other options won't;
4. easier on your back, assuming it's you who have to schlep the batteries;
5. better availability worldwide...a key factor for cruising sailors;
6. faster charging, lower run times for engine and/or generator; and
7. endorsement by experienced sailor-engineers such as Calder and Verry.
Providing that the installation is a good one, the potential "downside risks" of paralleling batteries are few and, in my experience and reading, very remote. This is particularly true because the "paralleled battery installation" itself, with reasonable care and attention to battery maintenance, is likely to reduce the downside risk of, e.g., a shorted cell by reducing the degree of sulphation and by maintaining a higher state of battery health.
A final factor...then I'm done. You can never discount the human factor, and the ability of a tired or careless or ignorant sailor to inadvertently murder his batteries. By keeping the system simple: one house battery bank only, one voltage measurement only, one charging rate only, etc..... you significantly reduce the chance of this happening.