If you increase numbers, you'd still have to find the people to supervise students attending the scheme which may be even more difficult logistically with everyone working from home.From what I heard, firms aren’t increasing the number of people interviewed etc.
Personally, I do wonder why in light of vac schemes being done online, firms don’t do more vac schemes or offer more places? I do understand that the number of TC in the end are most likely the same as previous years, but vac schemes are so important that firms could have easily increased their capacity at least until things go back to what they used to (if they ever do).