A flint and steel in a dispenser should ignite a creeper

When you right click a creeper directly with a flint and steel it ignites it. This behavior is similar to right clicking a sheep with shears and it dropping wool. 

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All the other functions of the flint and steel that you can do by hand like lighting a fire or activating a nether portal can be done by dispenser except igniting a creeper. 

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The dispenser already has a similar function with the shearing of sheep namely the dispenser interaction with an entity in front of it in a specific way depending on the item inside the dispenser 

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One reason the game needs despensers igniting creepers is to replace tnt duplication as a way to automatically destroy blocks

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A second reason specific to bedrock is that it follows intuitively from the fact that dispensers can do everything else with flint and steel you can and they can interact with entities... This would be intuitive similar to C4pistons moving tile entities like chests. 

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