Segment transparency reduces your flexibility to shuffle data around when things turn ugly. You want to use selective transparency only when the metrics are in your favor, otherwise you should make analyzing your company as difficult as possible in order to turn people off from actually looking under the hood. For example, unlike every other auto manufacturer Tesla Motors does not report monthly sales data by country. This obfuscation of data allows imagination to take over and analysts can project all kinds of irrational hopes and dreams onto the company's actual results. If you are rolling out a new product country-by-country, but only reporting aggregate sales, it makes it unclear how your sequential and year-over-year sales comparisons look. Teslas's situation is the equivalent of a retailer opening new stores rapidly, but only reporting total sales and not same store sales comps and this provides the illusion of growth when in fact it has the worst growth of any auto maker in the US.
As your operating results and certain metrics move in the wrong direction, slowly disclose less and less and simultaneously shift the focus to a different metric which is not yet eroding. Another tactic to utilize is to consolidate segments when growth in key areas is declining. If things stabilize again, you can unwind the segment consolidation a few quarters/years down the road, or cherry-pick good data to share that is not verifiable from looking at your reported segment data (e.g. "Article in @WSJ re Tesla sales is incorrect. September was a record high WW and up 65% year-over-year in North America.").
Should you wisely choose to limit important disclosures, the most common scapegoat is the competitive landscape. Simply state that you don’t want your competition to know the margins of a certain segment or its sales growth, etc. What you can say is that disclosing the data the investor is requesting could potentially shed light on how amazingly profitable that segment is due to your exciting new products and competitors might use that information in their own price negotiations or in leveraging your customers to switch over because you are making so much money off their backs. This is, of course, a bogus reason, as your competition already knows everything there is to know about your business. Another reason to not have better disclosures would be that you fear analyst can't analyze the data well due to its lumpiness, seasonality, or whatever else you can think of that patronizes and insults the market's intelligence (I for one, can't blame you).