A company has an expense process. You have a card. Tools get bought mid-project because a client needs something delivered on Thursday, charged to whichever account was convenient, and never sorted afterwards. The result is one undifferentiated stream of recurring payments where roughly half are deductible and nobody knows which half.
Income is irregular; the subscriptions are not. A fixed monthly tooling cost is easy to carry in a good month and genuinely painful in a slow one. Knowing the exact number is what lets you decide which tools are worth keeping through a quiet quarter.
Deductions go unclaimed because the list is incomplete. Most freelancers can name their three biggest tools and forget the six small ones. Those six are real business expenses, and they are only missing from the tax return because they were missing from the list.
Client-driven tools accumulate. One client wants files in a specific format, another uses a particular platform. Those subscriptions outlive the projects that justified them, because cancelling requires remembering they exist.