Here is an old quote from Tim Vandergrift (WE rep). It's from 2005 but I've seen the same response from him in various forms over the last several years.
"Most wine kits designed to make dry table wines (such as most reds and Chardonnay--the two varieties that get malolactic when made commercially) do not require acid additions of any kind, either tartaric, malic, or citric. The juices and concentrates contain enough acid as-is.
The fact of the matter is that Winexpert kits are perfectly balanced for acidity at packaging. A successful malolactic fermentation would change this balance unacceptably, leaving a kit flabby and weak tasting. If I re-balanced a kit for malolactic (higher levels of all acids, plus nutrients and higher pH) it would taste rather horrible without malolactic!
(Most of the time you can't get a malolactic fermentation going in wine kits, due to the low pH and nearly-absent levels of dissolved solids and nutrients, both of which malolactic bacteria require to grow).
In addition, the use malolactic bacteria is complex and fraught with danger for the bulk of people who buy and use wine kits. To control it correctly you need a malolactic chromatography kit, ($75.00+) and the skill to use it. Fine if you like that sort of thing, but most people (i.e., 99% of the people who buy kits) may well be happier without it. "