cinnamon
That model (sole custody with fortnightly visits with NRP) was the standard of the 70's and 80's as divorce rates increased dramatically and became accepted as 'the norm' through convention, not because it had been shown proved to be best for children.
I disagree that it became 'the norm' through convention. It became 'the norm' because for most families, it is the most practical solution, as policy briefing from the Nuffield Foundation shows.
Equal (or near-equal) parenting time has been found to be one of the most fluid patterns of care, typically converting into more traditional arrangements, which is perhaps not surprising given the logistical and relational challenges of shared time.
Despite the gradual increase in shared time arrangements post separation they remain unusual, both in countries without legislative intervention like the UK and in countries that have legislated to encourage it
Indeed the table on page 3 of the policy briefing shows that shared care (50-50) in the UK is estimated to take place in 3.1% of separated families. Even in Sweden, often held up as the "gold standard", it is only estimated at 28%.
You say it may be, in a some cases, that EOW is what is best for a family, but overall when you look at the outcomes of thousands of children, it has problems
I'm not sure what you're basing that statement on. It is separation, the resulting financial impact and ongoing parental conflict which causes "problems". From the same study:
Research shows that the best interests of children after parental separation are most strongly connected to the quality of parenting they receive, the quality of the relationship between their parents, and practical resources such as adequate housing and income ? not to any particular pattern of care or amount of time (Irving & Benjamin 1995a; Lye 1999; Moyer 2004; Pryor & Rodgers 2001; Shaffer 2007; Smyth & Wolcott 2003).
Most telling is this analysis on page 8:
We also know that children often feel responsible for their parents? happiness, believe they should share themselves and want to avoid parental conflict. As a result, children who are unhappy with their shared time arrangements may be very reluctant to raise the possibility of changing those arrangements (Cashmore et al 2010; Haugen 2010; Neale et al 2003; Singer 2008; Tucker 2006).