Why don't shipping businesses own their own shipping containers? About two or three years ago I attended a talk by a consulting statistician, one of whose clients was a company in the business of leasing out intermodal shipping containers.  He said those who are in the business of using those containers to transport goods typically do not own the containers, but pay a company such as his client for their use.  They pay rent periodically forever and don't normally ever return the containers to the permanent owner.

My question is: Why is it done that way?  Why not buy the containers if you're going to use them for as long as you're in business?

(The occasion for the speaker's experience of this phenomenon was that Congress passed a bill granting tax deductions to companies whose containers are used in U.S. commerce rather than being used only, for example, to carry things back and forth between South Africa and Australia, etc.  Companies could not claim the tax deduction unless they had records indicating how many of their containers were used in U.S. commerce, and they had no records at all of where their containers had been because they hadn't expected Congress to pass such a measure.  Trying to get the information about where each container had been was far more expensive than what they'd save in taxes, and in many, maybe most, cases, the shipping companies didn't have the information at all.  So the consulting statistician and a colleague came up with a theory: For tax purposes, intermodal shipping containers are fungible.  They didn't need to know which containers had been where, but only how many with the company's logo had entered and left the U.S.  It turned out that information could be acquired inexpensively from port authorities. The company argued that that would underestimate the number of the company's containers used in U.S. commerce, since, for example, ships that transport wool from Australia to China to be made into sweaters to be sold in the U.S. were engaged in U.S. commerce when the retailer in the U.S. paid for the transportation.  The IRS accepted the fungibility theory and allowed the deduction.)
First, it appears there are historical reasons: it was the initiative of the producers to standardize the way their goods were transported, already from the factory. And it involved transportation by rail initially, rather than ship. See interesting information here.

Second, I see an economic rationale: overseas commerce is rather volatile, especially at individual-shipping-company level. In such a situation, it would be difficult for each individual shipping company to optimize the number of containers owned. But if there are companies that lease out containers to all the shipping industry, fluctuations dampen and overall capacity is more easily optimized.

Another approach can be found here, where on the subject the authors write


  “Own or lease?” The question has long lain at the heart of container-shipping strategy. From our analysis, the industry typically
  relies too much on leasing. While leasing may be the only option for
  many cash-strapped liners that already have substantial debt, other
  lines should take advantage of this by owning more of their fleet.
  Leasing does provide a little more flexibility to change vessel
  deployment. But that breathing room often comes at too high a price.


The "substantial debt" usually comes from building/buying new ships.