Its pretty explicit in the agreement terms that you need to separately click to agree on every purchase:

> Valve hereby grants, and you accept, a non-exclusive license and right, to use the Content and Services for your personal, non-commercial use (except where commercial use is expressly allowed herein or in the applicable Subscription Terms). This license ends upon termination of (a) this Agreement or (b) a Subscription that includes the license. The Content and Services are licensed, not sold. Your license confers no title or ownership in the Content and Services

> F. Ownership of Content and Services

> All title, ownership rights and intellectual property rights in and to the Content and Services and any and all copies thereof, are owned by Valve and/or its or its affiliates’ licensors. All rights are reserved, except as expressly stated herein. The Content and Services are protected by copyright laws, international copyright treaties and conventions and other laws. The Content and Services contain certain licensed materials and Valve’s and its affiliates’ licensors may protect their rights in the event of any violation of this Agreement.

> G. Restrictions on Use of Content and Services

> You may not use the Content and Services for any purpose other than the permitted access to Steam and your Subscriptions, and to make personal, non-commercial use of your Subscriptions, except as otherwise permitted by this Agreement or applicable Subscription Terms. Except as otherwise permitted under this Agreement (including any Subscription Terms or Rules of Use), or under applicable law notwithstanding these restrictions, you may not, in whole or in part, copy, photocopy, reproduce, publish, distribute, translate, reverse engineer, derive source code from, modify, disassemble, decompile, create derivative works based on, or remove any proprietary notices or labels from the Content and Services or any software accessed via Steam without the prior consent, in writing, of Valve.

> You are entitled to use the Content and Services for your own personal use, but you are not entitled to: (i) sell, grant a security interest in or transfer reproductions of the Content and Services to other parties in any way, nor to rent, lease or license the Content and Services to others without the prior written consent of Valve, except to the extent expressly permitted elsewhere in this Agreement (including any Subscription Terms or Rules of Use); (ii) host or provide matchmaking services for the Content and Services or emulate or redirect the communication protocols used by Valve in any network feature of the Content and Services, through protocol emulation, tunneling, modifying or adding components to the Content and Services, use of a utility program or any other techniques now known or hereafter developed, for any purpose including, but not limited to network play over the Internet, network play utilizing commercial or non-commercial gaming networks or as part of content aggregation networks, websites or services, without the prior written consent of Valve; or (iii) exploit the Content and Services or any of its parts for any commercial purpose, except as expressly permitted elsewhere in this Agreement (including any Subscription Terms or Rules of Use).