Keeping in mind that there are many types of coverage and each individual consumer will have different specific insurance needs, there may be several reasons to consider consolidating your various policies with a single carrier. For most people, the pros of consolidation usually outweigh the cons, but here are some points from both sides:
Cost. Consumers often find there's a cost benefit in consolidating their coverage with a single carrier. While the exact number will vary from company to company, it's very possible to save 15% or more. Specialist companies still exist, but many generalist insurers have diversified their product lines to include an array of business and personal insurance and financial products. Since an insurance carrier is gaining customer loyalty and reducing their marketing costs when an existing customer purchases additional products, they're usually willing to pass a portion of their savings on to their consumers.
Gaps. Depending on the types of coverage you've purchased and your unique situation, certain coverage gaps could be reduced when you consolidate your insurance portfolio. Take purchasing General and Professional Liability through the same carrier as an example. An accountant, for example, would have little risk of their professional services leading to property damage or bodily injury, but a travel agent, for example, routinely makes professional recommendations that could have physical consequences for their clients. The travel agent might be unaware that a lodging they recommend to a client is undergoing renovations. The client slips and falls due to unsafe conditions and sues the travel agent for not knowing the condition of the lodging before recommending it. If the travel agent has General and Professional Liability through two different carriers, then he/she may find the two carriers pointing the finger in opposite directions and disclaiming coverage. Whereas, if the travel agent has both coverages under the same carrier, then the disclaiming concern is moot since there isn't another company to point the finger at.
Tailoring. Many carriers have learned to anticipate the common problems associated with coverage gaps, such as in the example discussed above. These carriers have created tailored packaged policies or programs with multiple different coverage options. These options interlock, but don't unnecessarily duplicate coverage or dangerously leave gaps between coverages. Umbrella policies perform best when written by the carrier of your primary coverage(s).
Cons. As with most everything in life, there are cons to consolidation. It's important that you look at the financial strength of the insurance carrier. If an insurance carrier is poorly rated by any of the rating services that monitor insurers, then the increased risk of going with an insurer that has questionable financial strength might outweigh any of the cost, gap, and tailoring pros.
Another con is that the insurer might quickly change their hunger for a certain product and leave you having to find replacements for multiple policies. Research the company's track record - have they typically stuck it out during bad and good times or have they timed the market to make a quick dollar and exit? Although most generalist insurers have diversified their offerings, it's possible to miss out on some coverage benefits still only being offered by specialists.
In closing, consider the above points and how each could or wouldn't meet your needs. In most cases, you'll find that coverage consolidation and the right carrier creates a winning scenario for all parties involved.