<p>That is because vanilla Keras does not include implementation of methods/models for object detection. </p>

<p>There are many approaches to object detection with deep learning (see <a href="https://arxiv.org/abs/1807.05511" rel="nofollow noreferrer">Object Detection with Deep Learning: A Review</a> for a survey), but none of them are implemented as a part of Keras library, so no official models as well. I have a feeling that François Chollet tries to keep it simple and minimalistic, so bloating the code with something like <a href="https://github.com/tensorflow/models" rel="nofollow noreferrer">TensorFlow models</a> will be against its philosophy.</p>

<p>However, Keras is easily extendable, so there are plenty of unofficial implementations (e.g. <a href="https://github.com/pierluigiferrari/ssd_keras" rel="nofollow noreferrer">SSD</a> or <a href="https://github.com/matterport/Mask_RCNN" rel="nofollow noreferrer">Mask R-CNN</a>) supplied with the trained models though. See <a href="https://modelzoo.co/framework/keras" rel="nofollow noreferrer">Keras model zoo</a> for more.</p>
pretrained object detection models in keras
<p>There are pretrained <strong>object recognition</strong> models in keras.applications library. But as far as I know, there is no pretrained <strong>object detection</strong> model available.</p>

<p>Does anyone know why it is the case? Object detection is a big part of problems when dealing with visual problems.</p>