Parturition - S2-E7
Question: Tom is showing Kes how to pilot a shuttle in the holodeck. Why did they use footage of Jem'Hadar fighters attacking?
Answer: As stated, the practical answer is to save money on effects. The in-world answer is that they could recreate the fighters from sensor records.
Answer: To help her prepare for threats and other obstacles that she may encounter while piloting a shuttlecraft.
My question is why did the show reuse footage from ds9 s3 of Jem'Hadar fighters attacking?
Answer: Because it saves on production costs.