Why does this phrase use 似的 instead of 似地？
"似的" is a fixed term/word, there is no "似地", so no matter how/where you use it (eg. after a verb or noun), the expression is always "似的".

You can still see "似地" in many places nowadays is mainly due to historical reasons. However based on the latest version of the official Chinese dictionary, the correct usage is alwyas "似的". If you use website that based on the latest official dictionaries, you won't find any "似地". e.g. cidian.xpcha.com  

Here are some detailed explanations. It is from 人民教育出版社 "People's Education Press(PEP)", the official publisher of the Chinese Dictionaries used in Mainland. The summary is in its last sentence: "无论什么情况，都不应将“似的”写作“似地”.", which means "No matter in what circumstance, you should only use “似的” rather than “似地”". 

One more quoted paragraph for the comment below:


  虽然也有一些语法书、辞书，如黄伯荣、廖序东主编的《现代汉语》(甘肃人民教育出版社1983年版)、王自强编著的《现代汉语虚词用法小词典》(上海辞书出版社1984年版)等有“似的”组成短语作状语时可写作“似地”的说法，但一般的现代汉语词典特别是权威性词典，都不收录“似地”这种写法，这在实际上是以“似的”为规范词形，而弃置“似地”这一写法。