Yes.
Since most people keep IAS itself as the first option, the representation of other services as first option among the top 100 also is less.
In my batch of IRS there were many people who had kept IRS as first option. However, they did not make it to the top 100 ( I am assuming you mean top 100 only as toppers ;) ). Not that it would have affected their prospects since IRS closes at around 370. The topper of our batch was Rank 105, which meant IRS IT was her second option. This you find a lot.
Two of my Juniors Bipasha kalita ( Rank 41) ShreshthTayal ( Rank 73) are examples of people who kept IRS IT as first options.
There are some people in the previous year allocation lists also, whom you can see had kept IRS IT, IPS, IFS as first options.
If I have misunderstood the question,i.e if it asks for only the first rank, it has been mostly IPS or IFS only I guess.