Most of the records on Rootsireland would have been transcribed during the 1980s/90s, so they probably chose a 70 year cut off. Most of what I've seen only goes to about 1910 in fact.
If you did follow up by asking Rootsireland if they intend to add new records for later periods, please let us know what the answer was. I haven't heard of them replying to queries at all.