This may have been why Jesus implied He might not find faith when He returned.
You might want to take context of that verse into mind: Saying it's because people don't believe Daniel is a preterist book is certainly not its point.
Luke 18:
1 And he spake a parable unto them to this end, that men ought always to pray, and not to faint;
2 Saying, There was in a city a judge, which feared not God, neither regarded man:
3 And there was a widow in that city; and she came unto him, saying, Avenge me of mine adversary.
4 And he would not for a while: but afterward he said within himself, Though I fear not God, nor regard man;
5 Yet because this widow troubleth me, I will avenge her, lest by her continual coming she weary me.
So first, the point of the Parable: That you should continue praying even when it seems like your prayers are not heard or answered when in duress, particularly, under persecution from an adversary. This widow was under duress, and she sought the judge's help, over and over and over.
Until he finally acquiesced and helped her.
Now see how the Lord applies this parable:
6 And the Lord said, Hear what the unjust judge saith.
7 And shall not God avenge his own elect, which cry day and night unto him, though he bear long with them?
8 I tell you that he will avenge them speedily. Nevertheless when the Son of man cometh, shall he find faith on the earth?
That before Jesus comes, His people will be under duress, under tribulation, and they will pray, and pray and pray, but along the way, some will not be patient, and will fall away (or be martyred)
We see Him go through this concept in the Olivet discourse in Matthew 24 and 25:
12 And because iniquity shall abound, the love of many shall wax cold.
13 But he that shall endure unto the end, the same shall be saved.
People will lose faith over time.
He shows it in a parable too
48 But and if that evil servant shall say in his heart, My lord delayeth his coming;
49 And shall begin to smite his fellowservants, and to eat and drink with the drunken;
50 The lord of that servant shall come in a day when he looketh not for him, and in an hour that he is not aware of,
51 And shall cut him asunder, and appoint him his portion with the hypocrites: there shall be weeping and gnashing of teeth.
People lose patience, and fall away.
Paul expresses the same
2 Thessalonians 2
1 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,
2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
1 Timothy 4
1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;
People lose faith during long stretches of hard times, especially persecution.
That is why the Lord muses about finding faith on the Earth when He returns, because He knows many will fall away when the times get really tough. Especially during the 70th week of Daniel.
It has nothing to do with people not agreeing with you that Daniel is history rather than prophecy.
Especially when He himself said that people in the future would see the Abomination of Desolation from Daniel 8, 9, 11, and 12. How that was supposed to be History .. did Jesus get it wrong, did Jesus interpret Daniel incorrectly and it was all in His past?
I don't think so, not when He quotes it.