[x87678r]

> It's job security and furthermore if it's a valuable piece of the product then it can keep praise and rewards centered on you.

That's part of it, but training people is also very difficult. If you know a system well it takes a day to add some feature, but it takes a few days of frustration to train someone else.

[kqr]

If those are actual numbers (a day versus a few days) then that should be an incredibly easy decision. A few extra days is nothing compared to doubling your capacity to deal with problems in that system!

[x87678r]

That is a few extra days for one task. 6 months later you'll still be training the person, though the overhead will still be lower it still will be slower than doing it yourself. Then the person might leave and you start all over again.

[kqr]

This seems like the common mistake of trying to optimise for individual efficiency at the expense of the rest of the system.

Yes, overhead will be higher, but since capacity also will be higher, cycle time will go down much more (non-linear effect) and you'll extract important value and feedback out of the tasks sooner, easily paying for further capacity improvements.