I already have too many places where analytic data lands up. I can see a business case in building tools to help me consolidate the data in my facebook engagement stats, my SEM referrals, my email clickthrough rates, my ad impressions, and my page level analytics.... but I don't see why I want to reflect single events into multiple analytic services. Maybe it's because I work with an analytic solution that just captures arbitrary events so I can just log everything in one place, so I'm missing the problem with working with services that are less flexible.
for example:
mixpanel and kissmetrics are great for tracking custom events and learning deeply about engagement and conversion inside your app.
but you're still going to want hittail or google analytics to analyze your referrers.
and you probably want customer.io, vero, mixpanel or klaviyo to do targeted email marketing, which is great for improving activation and retention.
so i'd say why wouldn't you want to use multiple analytics services? maybe our definition of "analytics" is just broader :)