Why don’t all managers develop their teams?!

𝐖𝐡𝐲 𝐝𝐨𝐧'𝐭 𝐚𝐥𝐥 𝐦𝐚𝐧𝐚𝐠𝐞𝐫𝐬 𝐝𝐞𝐯𝐞𝐥𝐨𝐩 𝐭𝐡𝐞𝐢𝐫 𝐭𝐞𝐚𝐦𝐬?! Earlier today, I was discussing leadership development programs with a prospective organization. The leader said that they have programs to develop first-time managers but are challenged with some of those managers not developing their own teams.

Why? There's probably a variety of reasons ...