I think XMR's emission after all the coins have been mined will actually help in adoption, encourage a bit of spending and could have a wider distribution than BTC.
Pure deflation would encourage more hoarding, less spending and could even cause the economy to stagnate.
Many are afraid of tail emission from wrong reason. And even from perspective of that reason they are wrong since in the next 10 years Monero will have lower inflation then Bitcoin.
Bitcoins inflation will be higher then of Monero from the year 2020 to 2025. After 2025, when Monero and Bitcoin inflation will even again, will Bitcoin slowly start realizing why Monero choose tail emission. It is not because of any economic reason but technical. Solving a problem that Bitcoin still need to solve.
The Cryptonote guys, whoever they are, prolly mostly thought it was very important in keeping the source of the blocks, aka the miners, interested in doing their job. But what they didn't realize was its effect on Monero's economy, which I think is mostly positive due to the reasons stated above.
The users need money in their pockets to encourage spending, hence creating a growing economy. Something that won't happen in a pure deflationary currency that encourages hoarding.