Why do I need to call detectChanges() with the default change detection strategy?

I am working on an Angular 4 app, but I am having a problem inasmuch as I am having to call this.changeDetectorRef.detectChanges(); to update the view when the model changes. For example, I have this code which is for pagination:

changePage(pageNumber) {
  this.currentPage = pageNumber;
  // why do I need to do this?
  this.changeDetectorRef.detectChanges();
}

I have expicitly set the change detection strategy on the component to ChangeDetectionStrategy.Default but this has no effect. It is happening here too when subscribing to an observable:

showResults(preference) {
  this.apiService.get('dining_autocomplete/', `?search=${preference}`)
    .subscribe((results) => {
      this.searchResults = results;
      // why do I need to do this?
      this.changeDetectorRef.detectChanges();
  });
}

If I console.log() this.searchResults in the TypeScript, I get the expected results, but if I use {{ searchResults }} in the HTML, it doesn't update until some other event happens, presumably when it goes through another digest cycle.

What could be going on?

== EDIT ===========================================================

The code for my component looks like this:

import {ChangeDetectorRef, Component, Input, OnChanges} from "@angular/core";

import * as _ from 'lodash';

@Component({
  selector: 'dining-search-results',
  templateUrl: './dining-search-results.template.html',
  styleUrls: ['./dining-search-results.style.scss'],

})
export class DiningSearchResultsComponent {
  @Input() searchResults: any[];
  @Input() hotTablesOnly: boolean = false;
  @Input() memberBenefitsOnly: boolean = false;

  numberOfTagsToDisplay: number = 3;
  resultsPerPage: number = 5;
  currentPage: number = 1;

  constructor(private changeDetectorRef: ChangeDetectorRef) {
  }

  get filteredResults() {
    return this.searchResults ?
      this.searchResults.filter((r) => !((this.hotTablesOnly && !r.has_hot_table)
        || (this.memberBenefitsOnly && !r.has_member_benefit))) : [];
  }

  get pagedResults() {
    return _.chain(this.filteredResults)
      .drop(this.resultsPerPage * (this.currentPage - 1))
      .take(this.resultsPerPage)
      .value();
  }

  get totalPages(): number {
    return Math.ceil(this.filteredResults.length / this.resultsPerPage);
  }

  getInitialTags(tagsArray: any[], count: number): any[] {
    return _.take(tagsArray, count);
  }

  changePage(pageNumber) {
    this.currentPage = pageNumber;
    // why do I need to do this?
    this.changeDetectorRef.detectChanges();
  }
}

When changePage() is called, and this.currentPage is updated, the changes are not reflected in the HTML unless I call detectChanges().