Many tubers and parents are not aware of alternatives to the traditional and more frequently-prescribed corn syrup-based formulas. Because these formulas are a long way from "real food," they can cause or worsen health issues such as diabetes and GI discomfort, which is often why other options are sought.
Of course, blending "normal food" + liquid in a high-power blender is the ideal. However, not everyone has the time for this, and most people want to eat outside the home, where refrigeration may not be available, at some point.
Check with each manufacturer, medical supplier and/or your health plan about reimbursement. Each is on some "approved lists," but none is on all. Regardless, with a physician's order (and documentation if/as required, e.g. by Medicare), you may be able to obtain coverage.
There are three companies making commercially-available alternative tube food at this time -- please note in Comments if you know of another.
Kate Farms® (two fortified Core Essentials varieties, can be used orally or through tube)
Real Food Blends™ (blenderized food, not fortified, so supplement with multivitamin and salt if used alone, probably requires thinning)
Nutrition and hydration are more than feeling satisfied after a meal or energy to do things. The right fuel can make all the difference to everything from breathing to skin health and pressure ulcer risk.